The clouds and mist of Mount Zhongnan coiled around the mountainside. Zhang Yifan followed the man in grey into a vine-covered cave, only to stumble over a protruding bluestone—carved upon the stone was half an ox, its horns pointing toward the Big Dipper constellation pattern on the cave ceiling. "The 'Tian shu Formation' set by the Grand Master," the man in grey said in a low voice, "requires the Taiji Double Pendants to stir the earthly veins."
The youth rubbed his knee with a mischievous grin, pulling out a wooden ox model that Huwa had stuffed into his pack: "Want to try this?" He placed the model right in the center of the star pattern, and the mica flakes inside the ox's eyes suddenly reflected the light, casting the characters "Taichu" and "Taisu" onto the cave wall. The man in grey froze as he watched Zhang Yifan turn the gear on the ox's tail. The model let out three low "moo"s, and stone dust showered down from the cave ceiling, revealing a hidden door—it turned out the Grand Master's intricate mechanism had been cracked by a village boy using a toy ox.
The secret chamber was piled high with rotting account books, and a bronze tripod in the corner was engraved with the "Nine Rules of the Merchant Path." Buried beneath the tripod was none other than the golden seal of the Taiji Chamber of Commerce. Just as Zhang Yifan reached out to touch it, he heard a cough from the shadows. Three white-haired elders walked out leaning on abacus frames, their waist pendants carved with gold, wood, and water Taiji motifs respectively.
"A wet-behind-the-ears brat dares to touch the Chamber's token?" the elder surnamed Jin sneered, his abacus beads clicking away briskly. "When the Grand Master fell, you were probably still wetting the bed." Zhang Yifan remained unruffled, pulling seven seeds from his bamboo basket and scattering them before the tripod: "Does the elder know that these 'Cyan Ox Seven' can take root in the Gobi Desert, and the millet they yield, when boiled into porridge, is thirty percent thicker than the tribute rice of Chang'an?" He suddenly pointed at the money pouch at the man in grey's waist: "When we entered the mountain just now, I slipped a Granary-Guard Beetle Shell into your pouch. If the beetle crawls toward the 'Gold' tripod right now, we'll know your ledgers are short thirty percent on sesame imports."
The elder's expression shifted, and sure enough, he saw the beetle shell wriggling toward the bronze tripod. The elder surnamed Water narrowed his eyes: "Even if you know a thing or two about bugs, the Tea Horse Road has been monopolized by foreign merchants for a decade. What brilliant strategy do you have?" Zhang Yifan flicked his abacus, the beads falling into the four characters "Wooden Ox and Gliding Horse": "We transport with improved wooden oxen. Each ox carries a hundred catties of tea, yet consumes only a third of the forage of a foreign merchant's camel." He suddenly pulled out a cyan ox sachet embroidered by Xiaoxiu: "And if we sew this sachet onto the tea packets, not only does it prevent moths, but it gives foreigners the fragrance of Tianshan melting snow—they love that sort of novelty."
The three elders exchanged glances. The elder surnamed Jin suddenly swung his abacus at him, only to see Zhang Yifan flick his wrist and hurl three abacus beads, which struck with a series of clangs right into the "one, four, seven" positions of the opponent's abacus—precisely the "Wealth-Breaking Acupoint" from the "Cyan Ox Thirteen Calculations."
"Don't be hasty, Elder," the youth blinked. "These abacus beads of mine were soaked in peppermint juice. Your abacus won't be able to calculate interest for three days, which gives you just enough time to hear me out."
The oil lamp in the secret chamber flickered, casting its light on the treasures Zhang Yifan pulled from his bamboo basket: bamboo tubes carved with insect-repelling patterns, moisture-measuring Granary-Guard Beetle Shells, and spring-loaded wooden clog models made by Huwa.
"Foreign merchants monopolize 'brute force,'" he tapped the wooden ox model, "but we have 'ingenuity.' Take the gears of this wooden ox, for instance. Made from Qinling iron-birch wood, they are five times more wear-resistant than the oxhide axles of foreign merchants. Or take the Spring-Guiding Insects; placed inside tea bricks, they automatically seek out dry spots, making them a hundred times more hassle-free than camel caravans."
The elder surnamed Water chuckled softly: "It sounds rather like moving the hearth mechanisms of Cyan Ox Village straight onto the trade route."
Zhang Yifan nodded: "The trade route is like a hearth; everything depends on 'heat control.' Foreign merchants care only for profit, so we'll calculate the long-term accounts with them: this year we deliver ten carts of Cyan Ox tea in exchange for them opening three Gobi relay stations; next year we sell a hundred wooden oxen and gliding horses, freeing up half their caravan's transport capacity." He suddenly flipped open the "Classic of Hundred Insects" to the page illustrating ants moving a mountain: "Look, even ants know how to band together. If our Chamber of Commerce is less united than the children of Cyan Ox Village, wouldn't people laugh at us?"
The stone door of the secret chamber suddenly swung open with a rumble, and a Persian lad ran in through the morning light, clutching Zhang Yifan's wooden ox model to his chest: "Young Master! My master says he is willing to trade ten carts of colored glaze for the blueprints of your 'Iron-Biting Ox,' and throw in the secret recipe for Dashi Country cumin as well!"
Zhang Yifan raised an eyebrow and shook the tail of the model at the three elders: "You see, foreign merchants are even more impatient than we are."
The elder surnamed Jin looked at the jade pendant at the youth's waist and let out a long sigh: "When the Grand Master said back then, 'The revival of the merchant path lies with the Cyan Ox,' I thought it was merely a riddle, never expecting it to land on a mud-legged country boy like you." He took out the Chamber's golden seal and pressed it heavily onto the "Cyan Ox Seven" contract handed over by Zhang Yifan: "The Western Regions trade route is yours. If you lose capital..."
"I won't lose!" Zhang Yifan shoved the golden seal into his bamboo basket, conveniently pressing it down on top of Xiaoxiu's osmanthus sugar cakes: "I've written it clearly in the contract: if the foreign merchants default on their debts, I'll scatter 'itching powder' into their camel caravans—Huwa calls this 'an eye for an eye, a camel for a camel.'"
When the clouds and mist dispersed, a string of strange footprints was left on the stone steps of Mount Zhongnan: on one side were the cloth-boot prints of the Chamber elders, on the other were Zhang Yifan's straw sandal prints, and mixed right down the middle were the gear tracks of the wooden ox model. The mountain wind brushed past his lapels, revealing the cyan ox pattern stitched inside—one that Xiaoxiu had embroidered overnight, clumsy in its stitches yet filled with warmth, making him feel far more secure than any token of the Chamber of Commerce.
As the first sound of camel bells rang out beyond the walls of Chang'an, Zhang Yifan touched the "Cyan Ox" beads on his abacus and smiled. This trip to the secret chamber had not only won him the golden seal of the Chamber of Commerce, but also made off with the raisins the elders had hidden away—just as he often said back in Cyan Ox Village: "The merchant path, you see, is like a roasted sweet potato: charred on the outside and tender within, with the sweetness hidden in the most solid place." And the new story belonging to the Taiji Chamber of Commerce, carried by this youth clutching abacus beads and seeds, was now taking its first footprint scented with fresh grass along this thousand-li tea route.