"Princess Consort, what do you think of this?"
"Yes, not bad. This is the effect I wanted."
Qin Lu had just reached the courtyard gate when he overheard the conversation inside.
Even without seeing Gu Yanshu yet, the approving tone in his voice told Qin Lu that progress had been made.
Looking up, he spotted a craftsman holding a piece of glass in front of Gu Yanshu, who stood with his back turned, still engrossed in discussion.
Gu Yanshu, unaware of Qin Lu's arrival due to his position and Qin Lu's light footsteps, continued instructing the craftsman:
"Later, you should—"
"This servant greets His Highness Prince Li!"
Before Gu Yanshu could finish, the craftsman caught sight of Qin Lu and immediately bowed in greeting, not waiting for Qin Lu to motion for silence.
"You're back?"
Gu Yanshu turned instinctively, spotting Qin Lu standing not far behind him. Glancing at the time, he seemed surprised.
"Your Highness seems to have some free time today?"
Lately, Qin Lu had been returning late at night.
Yet now, it was barely past Shenshi (around 3-5 PM).
Qin Lu nodded slightly, confirming Gu Yanshu's guess.
"Military affairs were mostly settled two days ago. Today was just tying up loose ends. Unless something unexpected happens, I should be able to return earlier from now on."
"It's good that Your Highness can come back sooner. The weather's getting colder—it's not good to be out too long."
Compared to Gu Yanshu's previous life, Tianqi's winters weren't particularly harsh, and snowfall arrived unusually late.
It was only a few days ago that Gu Yanshu had seen the first snow of the season.
However, Tianqi's lack of modern heating made the winters feel more unbearable in comparison.
Just as this thought crossed his mind, a cold gust of wind swept through, making Gu Yanshu shiver involuntarily.
Qin Lu unfastened his heavy cloak and draped it over Gu Yanshu's shoulders, chiding softly:
"Why is the Princess Consort outside today? And without even adding an extra layer?"
Though Qin Lu wasn't a muscle-bound brute, compared to him, Gu Yanshu could almost be described as "petite."
Wrapped in Qin Lu's cloak, Gu Yanshu was practically engulfed from head to toe.
Savoring the residual warmth from Qin Lu's body, Gu Yanshu first closed his eyes contentedly before explaining:
"I've been working on the silver mirror these past few days. The lighting indoors wasn't sufficient, so I came outside to check the effect. I was about to go back in."
Following his words, Qin Lu's gaze shifted to the glass in the craftsman's hands.
Only then did he realize it wasn't just glass—it was a mirror.
"This is the silver mirror you've been working on?"
"Exactly. Would Your Highness like to see?"
Gu Yanshu nodded slightly, bending down to take the mirror from the craftsman.
But before his fingers could touch it, Qin Lu had already reached out and picked it up himself.
Staring at his reflection, Qin Lu saw his own face with unprecedented clarity.
Though Gu Yanshu had mentioned days ago that silver mirrors provided sharper images than bronze ones, he hadn't expected this level of detail.
Every strand of hair, every weave in his clothing—even the fleeting surprise in his eyes—was captured perfectly.
Gu Yanshu appeared beside him in the mirror at some point, their figures now framed together.
"What does Your Highness think?"
"It truly is as clear as you said."
Seeing their reflections side by side, Qin Lu suddenly found himself reluctant to put the mirror down.
"No wonder it's consumed so much of your attention."
"The one expending effort isn't me," Gu Yanshu chuckled, shaking his head. "The craftsmen in the courtyard have worked much harder."
While Gu Yanshu had indeed been tinkering with various inventions lately, none were truly handmade by him.
Many ideas were based on rough concepts he'd never personally executed.
But this hardly posed a challenge for him.
As he'd told Qin Lu when introducing movable type printing—"Different trades require different expertise."
While Tianqi lacked soap, it had palm kernel paste and saponin-based cleansers.
By summoning craftsmen skilled in these areas and offering slight guidance, creating soap became a trivial matter.
With Prince Li's estate undergoing renovations, craftsmen of all trades were readily available.
This was how Gu Yanshu had managed to produce so many novelties in such a short time.
"The craftsmen have worked hard, but without the Princess Consort's ingenuity, they couldn't have created these."
Qin Lu didn't deny Gu Yanshu's words but swiftly pivoted to praise him instead.
Who doesn't enjoy compliments?
Gu Yanshu was no exception. He shot Qin Lu a glance, his lips curving into a particularly captivating smile.
The craftsman standing nearby had gone from trembling in Qin Lu's presence to speechless bewilderment:
Weren't the rumors about Prince Li being ruthless and frequently hanging the Princess Consort for beatings?
Then who was this man, draping cloaks over his spouse and fretting over him handling sharp objects?
Just as the craftsman was internally ranting, Gu Yanshu handed the mirror back to him along with quiet instructions:
"Take this for durability testing first. If there are no issues, inform Mr. Xin to produce several more silver mirrors using this method."
"Understood."
The craftsman hastily accepted the mirror and bowed before retreating.
"Mr. Xin?" Qin Lu raised an eyebrow at the familiar name. "Xin Quanyou?"
If he recalled correctly, Xin Quanyou was one of Prince Li's estate's retainers, wasn't he?
"The silver mirror isn't like those trivial items from before—it's worth far more. Naturally, I'd entrust it to someone reliable."
Gu Yanshu shot him a sidelong glance, immediately grasping his implication.
"What? Is there anyone in Prince Li's estate I can't use?"
"Of course not."
Qin Lu smiled faintly, wrapping an arm around Gu Yanshu's shoulders as he guided him indoors.
"If the Princess Consort wishes, this prince would gladly offer his services as well."
"Your Highness had better remember that."
Gu Yanshu lifted his chin arrogantly in response.
The braziers inside had been kept burning, and the moment they stepped through the door, warmth enveloped them.
Only Gu Yanshu's hands, chilled by the earlier wind, remained slightly stiff.
Seeing Gu Yanshu rubbing his hands together, Qin Lu stepped forward without hesitation, enveloping Gu Yanshu's chilled fingers within his own palms.
A faint surge of internal energy warmed his touch as he chided softly:
"Next time the lighting indoors isn't sufficient, just inspect items by the window. Must you really dash outside?"
While speaking, he motioned for Xingren to fetch a basin of warm water to wash Gu Yanshu's hands.
Knowing he was at fault, Gu Yanshu's earlier bravado vanished instantly.
"I was just... excited about finally completing the silver mirror," he mumbled defensively.
Unlike the previous small inventions that had progressed smoothly, the silver mirror had presented unexpected challenges.
Initially, Gu Yanshu had planned to use the silver mirror reaction—but producing the required silver nitrate proved difficult.
Forced to pivot, he resorted to a secondary method involving mercury.
However, mercury was notoriously toxic and difficult to control.
Only after repeatedly instructing the craftsmen on protective measures—avoiding direct skin contact—did he allow them to begin testing.
The first few attempts had been disappointing: either the reflections were blurry, or the mercury coating peeled off at the slightest touch.
It wasn't until today that they'd finally produced a satisfactory prototype.
In his exhilaration, Gu Yanshu had forgotten his cloak and rushed outside to examine it—
Only to be caught red-handed by Qin Lu, who'd returned unusually early.
Seeing Gu Yanshu's guilty expression, Qin Lu couldn't bring himself to scold him harshly.
The "warning" he issued was barely a reprimand:
"If there's a next time, don't blame me for assigning Xingren to shadow you relentlessly."
Recognizing the leniency, Gu Yanshu nodded eagerly.
"Understood! There won't be a next time!"
When Qin Lu handed him a bowl of ginger soup shortly after, Gu Yanshu wrinkled his nose at what he deemed an overreaction—
Yet he still obediently accepted it, downing the bitter concoction in one go.
By the time he set the empty bowl aside, Qin Lu's expression had softened noticeably.
Eager to steer the conversation away from his recklessness, Gu Yanshu seized the first diversion he could find:
"Enough about that—Your Highness should see this instead!"
Turning, he retrieved a small wooden box from inside the room.
Though fully aware this was a blatant subject change, Qin Lu indulged him, shifting his attention to the box.
Inside lay three objects.
One resembled a bamboo tube—its purpose unclear—while the other two were clearly crafted from glass produced at Taoran Kiln.
"What are these?"
Qin Lu picked up the handle-mounted item shaped like a tiny fan.
Gu Yanshu glanced at it and answered promptly:
"That's called a magnifying glass."
"Magnifying glass?" Qin Lu rotated it curiously.
"Here's how it works."
Gu Yanshu took it back, spreading his palm beneath the lens.
"Look, Your Highness—see how my palm lines appear enlarged?"
Only then did Qin Lu grasp its proper use.
Testing it on his own hand, he observed the same effect.
Though Prince Li's estate now housed numerous glass items thanks to Gu Yanshu, none could achieve this magnification.
The ingenuity impressed him, even if he didn't understand the principles behind it.
However, given Qin Lu's exceptional eyesight—honed to pinpoint accuracy on the battlefield—the magnifying glass held little practical value for him.
His interest soon drifted to the remaining two objects.
Noticing his gaze, Gu Yanshu lifted one of them—a framed set of glass lenses—and explained:
"These are spectacles. Didn't Your Highness mention recently that His Majesty's vision has deteriorated? And it's not just the emperor—many aging officials share the same struggle."
"Correct."
Qin Lu's nod carried dawning comprehension.
Gu Yanshu's next words confirmed his suspicion:
"Spectacles allow those with failing eyesight to see clearly again, just as they once could."
Intrigued, Qin Lu moved to try them on—
Only for Gu Yanshu to intercept hastily:
"Ah—wait! Your Highness's vision is flawless. Wearing these would blur your sight and likely induce dizziness. If you're curious, have the estate's aging accountants test them instead. Their feedback will be more meaningful."
Two of the estate's elderly accountants suffered from presbyopia and had assisted Gu Yanshu in fine-tuning the spectacles' design.
Realizing these weren't meant for him, Qin Lu set them down.
As he did, his fingers brushed against the final bamboo-like tube.
Curiosity piqued, he picked it up.
"And this?"
"Ah, this..."
Gu Yanshu's lips curved knowingly.
Neither the magnifying glass nor spectacles would captivate Qin Lu—but this was the pièce de résistance.
Deliberately pausing for effect, he waited until Qin Lu's interest was palpable before revealing:
"This is a telescope—a gift specially prepared for Your Highness."