The Vice Minister had barely finished his offhand remark before regret set in.
Yan Lide's head snapped up, and the Director's gaze fixed on him with an intensity that made his stomach drop.
"Director Yan, I was honestly just joking," the Vice Minister said, raising both hands in defense.
"No." Yan Lide shook his head slowly. "Old Chen, you might be onto something. Maybe the mud has simply been missing a framework."
Old Chen's face froze.
"I was afraid you would say that."
Yan Lide was already turning the idea over in his mind, and the longer he examined it, the more sense it made.
Before it cured, this strange cement mixture had the exact consistency of wet mud. So the engineering team had fallen back on the methods they knew best and spent days trying to build test foundations with traditional rammed earth.
But this gray cement was no Yellow River mud.
Assuming that ordinary dirt-packing techniques would suit a chemical mixture nobody had ever seen was a glaring blind spot, and somehow Yan Lide had walked right past it.
Watching his friend's expression shift, Old Chen realized that his casual suggestion was about to become one of Yan Lide's wild projects.
"Director, perhaps we should think this over carefully before..."
Yan Lide was already on his feet.
"Old Chen, thinking is what brought us here. Now we build."
He was a man of action, and the moment the solution clicked into place he raised his voice and called his scattered workforce to the center of the courtyard.
"Everyone, gather around!"
Tools clattered to the ground. Boots pounded across the dusty yard.
Within moments, a crowd of master artisans and junior craftsmen had packed into a tight semicircle around him.
Yan Lide laid out the new theory in three quick sentences.
Skeptical looks rippled through the crowd.
One of the older carpenters, a wiry man with sawdust permanently lodged in his beard, glanced at the cracked cement blocks and then at the proposed wooden framework.
"Director Yan, so we're putting wood inside the mud?"
"Not just any wood, Old Sun. A framework, something to hold the material together while it cures."
Old Sun rubbed his beard.
"And you're certain this will work?"
"No."
The carpenter blinked, and Yan Lide shrugged.
"That's why we're testing it."
A few artisans traded glances. Somebody snorted, somebody else laughed, and then the whole crowd grabbed their tools and went back to work.
This was the Directorate of Works, the nerve center of imperial engineering. Every man in the compound was either a master builder or a highly educated technical supervisor.
They all shared one simple philosophy about new ideas.
You never argued over a theory. You built it and watched to see whether it fell down.
The courtyard erupted into coordinated chaos.
Men shouted measurements across the yard. Saws ripped through fresh timber. Mallets drove wooden stakes into the hard ground.
Heavy posts went into the earth as deep foundation anchors. Once the desired thickness of the final wall had been worked out, flat planks rose on both sides to form a mold.
Then came the clever part.
Inside that hollow wooden shell, the carpenters set a tight, intersecting grid of rafters and purlins until the whole thing resembled the bare frame of a small house.
Old Chen watched them work for a while before leaning toward Yan Lide.
"Director Yan, if this actually works, I assume I'll receive some credit for the original suggestion."
Yan Lide did not even glance at him.
"Of course, Old Chen."
The Vice Minister smiled.
"Excellent."
"Right after I explain to the Emperor that you suggested burying rotten wood inside the wall."
The smile vanished.
"I suddenly find I'm much less interested in credit."
Yan Lide finally laughed.
"Too late. You already suggested it."
While the carpenters hammered their wooden bones together, a second crew went into motion without wasting a single word.
They mixed a fresh batch of iron slag cement slurry. Shovels bit into raw materials. Water splashed into the pit. The heavy gray mud churned until it reached the perfect consistency.
When the carpenters stepped back and declared the mold secure, the masonry crew moved in.
They hoisted their buckets of wet sludge and poured it straight into the top of the frame until the internal skeleton lay buried beneath the cement.
Yan Lide watched the last bucket empty and let out a long breath.
"Whether this works or fails, we'll know by tomorrow."
Old Chen surveyed the enormous structure they had just built and gave a tired smile.
"Considering how much timber we just buried in that thing, I sincerely hope you're right, Director."
"So do I, Old Chen. So do I."
The cement needed time to cure, and there was nothing left to do but wait.
The sun sat low on the horizon, and the men of the Directorate cheerfully wrapped up their shift. Before heading home, though, they needed to wash the corrosive gray dust from their hands.
Yan Lide stood near the main office with an amused expression.
A crowd of professional imperial engineers, men whose average age had to be at least 35, had somehow turned into a pack of hyperactive children.
They sprinted toward the far corner of the courtyard, shoving each other out of the way.
"Out of my way, Old Sun!"
"You had it yesterday, Zhang San!"
"That was yesterday! Today is my turn!"
That corner housed the Directorate's main drainage channel, and beside it stood a strange new contraption.
A heavy iron cylinder buried deep in the ground. A long metal handle rising from the top. A small iron pipe jutting out of its middle toward the open courtyard.
The footrace produced a single victor, a young engineer with a wide grin and dirt smeared across his cheek, who seized the handle in triumph.
"Form a single-file line! Step up and get your water!"
Clank. Clank. Clank.
He pumped the handle with tremendous enthusiasm, and a moment later clear underground water surged through the pipe and splashed out of the spout.
"Whoo! Cold! It's so cold!"
"Move it, move it, my hands are filthy!"
"Director Yan, do you want to go first?"
Yan Lide waved a hand.
"Finish up, I can wait."
It was a manual water pump.
With blueprints from the future texts, master blacksmiths at his disposal, and nearly unlimited raw materials, reproducing this piece of technology had taken hardly any thought. He had built a working prototype on his very first attempt.
The night before, he had delivered the first unit to the imperial palace, where Emperor Li Shimin had it installed at once.
The princes and princesses treated the machine like a magical new toy and spent the entire evening squabbling over who got to work the handle.
"Me next! Me next!"
"No, it's my turn! You went first last time!"
"That was the other pump!"
The machine was wildly popular, and it was also completely useless.
Neither Li Shimin nor Yan Lide could think of a practical purpose for it. Once the novelty wore off, a mechanical pump offered no real advantage over a wooden bucket tied to a rope and lowered into a well.
It did not create water from nothing, and it did not make the water any cleaner.
Worse, its internal parts required precision cast iron, which made the manufacturing cost absurd. Without the Directorate's bottomless budget behind the project, building one would be a financial nightmare.
If a wealthy merchant wanted one for his private courtyard, the cost of the iron and labor would exceed the price of a healthy Turkic slave.
Still, the future texts had praised the device to the heavens, so it had to be valuable somehow. The trouble was working out how to use it economically.
Since he had leftover cast-iron parts lying around, Yan Lide ordered his men to assemble a second unit right there in the Directorate courtyard.
His hope was that if hundreds of master craftsmen handled the machine every day, one of them would eventually stumble onto its true purpose.
So far the strategy had produced exactly one result.
The pump had become an expensive playground attraction.
He watched his men splash water over one another, sighed, and shook his head.
"All right, you lot! Five more minutes, and then I want this courtyard empty!"
A chorus of groans answered him.
"Director, just one more round!"
"No. Home, now. Your wives will come looking for me if you're late again."
Grumbling, the engineers finally dispersed and left the pump dripping in the fading light.
Yan Lide joined the back of the line and waited patiently for his turn. Then he washed the cement dust from his hands, dried them, and called it a day.
He left the Imperial City through the Hanguang Gate and turned south onto the bustling main avenues.
After 2 city blocks, a cut through the Taiping Ward, and a walk along the crowded streets of the Tongyi Ward, he reached his destination.
His private residence lay deep inside the Xinghua Ward.
The neighborhood sat in a remarkably strategic spot.
1 block to the west was the Yankang Ward, which had been the private playground of the legendary minister Yang Su during the Sui Dynasty.
These days, its largest and most luxurious estate belonged to Li Tai, the Prince of Yue, a sprawling compound the Emperor had gifted to his favorite son.
1 more block beyond the Prince's estate stood the West Market, the economic beating heart of the entire world.
In short, Yan Lide lived on absolute prime real estate.
He had gotten it through a mix of luck and aggressive financial planning.
Both he and his younger brother, Yan Liben, had served as minor officials under the Sui, so they knew the brutal reality of Chang'an's housing market all too well.
When the dynasty collapsed and the Tang took over, the capital fell into a brief period of chaos and property prices crashed.
The brothers seized the chance, pooled every copper coin they owned, liquidated their entire savings, and bought a modest courtyard house in one of the capital's most desirable wards.
Every evening on his way home, Yan Lide paused to look westward over the neighborhood walls, where the towering roofs of Prince Li Tai's estate rose above the rooftops.
Rumor had it that the Emperor doted on the young prince so much that he rarely allowed him to leave the palace, which meant Li Tai spent most of his nights among imperial luxuries while the beautiful estate down the street sat empty for much of the year.
Yan Lide stared at the vacant mansion, and the familiar pang of jealousy stirred in his chest.
"One day," he muttered, "I will live in a house where I don't have to listen to my neighbor sneeze through the wall."
He walked on, and his thoughts drifted back to the future texts.
He remembered reading about buildings that scraped the sky, enormous structures that housed thousands by stacking entire communities on top of one another.
With that kind of architecture, surely the people of the future never worried about housing shortages in their capital cities.
He glanced over the crowded streets of Chang'an and wondered whether a day would ever come when countless towers rose across the land, giving every family under Heaven a place to live and filling every street with happy faces.
It was a poetic thought, and Yan Lide immediately shook it out of his head and quickened his pace.
"Enough daydreaming, old man. Liben is waiting."
The two brothers worked in completely different government departments, and their daily lives could hardly have been more different.
Yan Lide thrived at the Directorate of Works. He loved the chaos of engineering, enjoyed solving problems nobody else understood, and had a habit of being the last man to leave the compound every evening.
Yan Liben, on the other hand, hated his current assignment. The moment his shift ended, he bolted from the office like a frightened rabbit, hurried home, and waited impatiently for his older brother so the two of them could finally sit down to dinner together.
Yan Lide pushed open the wooden door and stepped inside.
"I'm home!"
No one answered, and only the soft clatter of bowls drifted out of the kitchen.
He washed his hands a second time at the basin by the door, though the cold water did nothing to lift his mood.
Then he walked into the dining room, where the smell of boiled vegetables reached him before he had even sat down.
His wife, Lady Liu, was already at the table ladling portions into plain wooden bowls.
She glanced up, read his face in half a second, and said nothing, which was simply her way. She had learned long ago that her husband's complaints about food were never really about food.
Their son, Yan Xuansui, a boy of about 10, was already working through his bowl with the resigned determination of a child who knew that complaining only made his mother's face tighten.
Across the table sat Yan Liben.
His own children, Yan Kejian and Yan Jiabin, were too young to join the adults for dinner and had already been tucked into bed by the servants.
Yan Lide picked up his chopsticks and poked at a heap of boiled greens.
"Liu-er, if I have to eat like this every single day, I may as well walk over to the Chongde Ward next door and shave my head. I could become a monk."
Lady Liu did not even look up as she set another piece of vegetable in his bowl.
"Then who would fix the roof when it leaks, husband?"
Yan Xuansui snickered into his bowl, and Lady Liu shot him a look.
The boy straightened his face at once and studied his vegetables like they were the most fascinating thing in the world.
Yan Liben had heard his brother's complaint and slowly lowered his chopsticks.
He stared down at his own trembling hands.
The man who always smiled and always had a clever joke ready now looked ready to burst into tears.
Yan Lide saw the devastation on his brother's face and felt a wave of guilt wash over him.
"Liben."
He reached across and rested a hand on his brother's arm.
"Eat more. A vegetarian diet makes a man feel lighter and purifies the spirit. You'll live to a hundred."
Lady Liu glanced at her husband. She knew exactly why her brother-in-law refused to touch meat.
The rumors about Doctor Sun Simiao were terrifying, and Yan Lide had heard the whispers at the palace himself.
Doctor Sun demanded absolute anatomical perfection from his official medical illustrator. He made the artists stand beside him at the dissection table, put scalpel blades in their hands, and had them cut into cold corpses.
He made them peel back the skin with their own fingers, and he ordered them to reach into chest cavities and trace the exact shape and position of every organ.
Yan Lide shuddered just thinking about it.
"I would rather dig ditches for the rest of my life," he muttered to himself.
"What was that?" Lady Liu asked.
"Nothing. Just talking to myself."
A heavy hush settled over the dining room.
The brothers chewed their boiled vegetables without a word, and Lady Liu refilled their teacups, her hand resting briefly on her husband's shoulder as she passed.
When the meal ended, the servants came in to clear the bowls, wipe down the table, and set out two steaming cups of hot tea.
They bowed and withdrew, taking the children out to play in the courtyard.
Now the brothers were alone.
Yan Lide took a sip of tea and looked at his traumatized younger brother with deep sympathy.
"Liben, when exactly will those anatomical drawings be finished?"
Yan Liben understood the protective instinct behind the question. His older brother had always been this way, gruff on the surface but forever watching and ready to step in.
He hesitated and bit his lower lip hard.
Then he reached under the table, drew out a thick stack of rough paper, and slid it carefully across the wood.
"Brother, I drew these over the past few days, in the little free moments I had."
His voice was barely a whisper.
Yan Lide frowned in confusion, set down his teacup, and picked up the stack.
They were casual sketches, drawn with a hard stylus instead of a soft brush, on small sheets of cheap paper, and the subjects were thoroughly mundane.
Ordinary people in simple line drawings. A man sitting on a chair, a woman lying on her side, a child running, a laborer leaping.
It was the most basic figure drawing imaginable.
There were about 8 pages in total, and Yan Lide flipped through them so fast that he reached the bottom in under 10 seconds.
Then he stopped and gasped sharply.
He turned the stack over, went back to the first page, and leaned in until his face was inches from the paper, studying the lines slowly.
A huge smile spread across his face, and a surge of fierce pride for his brother swelled in his chest.
"Liben."
His voice cracked.
"Your grasp of the brush, your path in painting... you have reached an entirely new level of mastery!"
These sketches were something else altogether.
Raw, undeniable power radiated from the cheap paper, and even simple drawings of running children and seated men were rapidly closing in on the flawless artistic style they had witnessed on the magical screens of the future texts.
The bodies had weight. The limbs moved with mechanical logic. The clothing draped over real physical structure instead of hollow outlines.
Yan Lide looked up from the pages and fixed his younger brother with burning curiosity.
"Liben. How?"
Yan Liben met his gaze.
His face was a twisted mask of tangled emotions, horrified, exhausted, and deeply enlightened all at once.
"My skills improved," Yan Liben whispered into the hush of the room.
"I owe it all to Doctor Sun."