A few days later, Fei Qian truly didn't expect that Li Ru would recommend him to Cai Yong.
Speaking of Cai Yong, he was truly a remarkable figure among scholars. Any one of the titles he held could easily dazzle the average person.
A great litterateur, historian, musician, painter, and calligrapher of the Eastern Han Dynasty—with so many titles, one couldn't help but wonder if Cai Yong was even human.
In literature, Cai Yong's most famous contribution was the *Xiping Stone Classics*.
During the reign of Emperor Ling, Cai Yong believed that many Confucian texts contained numerous misinterpretations and errors. To prevent misleading future scholars, he petitioned to correct these texts. After receiving imperial approval, Cai Yong personally inscribed the corrected texts on stone tablets, which were then erected outside the Imperial Academy. A total of 46 tablets were created, collectively known as the *Hongdu Stone Classics* or *Xiping Stone Classics*. These tablets served as the standard for scholars to correct their texts, and for a time, the entrance to the Imperial Academy was bustling with activity. Every day, crowds of people came to view and copy the inscriptions, with carriages and horses numbering in the thousands, often blocking the roads.
In music, aside from the famous story of the *Jiaowei Qin* (a zither made from scorched wood), Cai Yong also composed the *Cai Family Five Tunes*: *Spring Outing*, *Clear Water*, *Deep Thoughts*, *Sitting in Sorrow*, and *Autumn Reflections*. These, along with the *Four Tunes* composed by another great musician, Ji Kang—*Long Clarity*, *Short Clarity*, *Long Side*, and *Short Side*—were collectively known as the *Nine Tunes*. After the Han Dynasty, they even became part of the imperial examination system for selecting officials.
Of course, later generations also took an interest in Cai Yong partly because of his daughter, Cai Yan (Cai Wenji), but that's a story for another time.
So, when Li Ru informed Fei Qian that he had recommended him to Cai Yong, Fei Qian could hardly believe it. Even as he entered the Cai residence, he still felt as if he were in a dream.
Cai Yong, seated in the main hall, was also unsure how to handle the situation. He hadn't taken on any disciples for many years. First, his reputation had grown, and accepting disciples required careful consideration. Second, the unfortunate events involving his daughter had left him somewhat disheartened. Third, as he aged, he no longer had the energy to devote to teaching, so he had simply stopped accepting disciples. But now, Li Ru had somehow found a token Cai Yong had given to a friend years ago and sent it back, with the condition that Fei Qian be accepted as a disciple. This put Cai Yong in a difficult position.
When Li Ru sent the token, he had been casual yet clear, explaining that Fei Qian's father had once done him a great favor. Now that he had achieved some success, he learned that Fei Qian wished to pursue learning and thus used his connections to retrieve Cai Yong's token. Whether or not Cai Yong accepted Fei Qian was up to him, but Li Ru had done his part and could rest with a clear conscience.
The key phrase here was "a clear conscience." While Li Ru could rest easy, if Cai Yong refused, he would be going back on his own words: "Whoever brings this token, if it is within my power, I will not refuse." How could he then claim to have a clear conscience? If word got out that Cai Yong had broken his promise, how could he continue to maintain his reputation?
Cai Yong looked at the young man in the hall. He was tall, with a reserved demeanor and a refined appearance—passable, at least. But whether or not to accept him as a disciple left Cai Yong feeling conflicted. Still, since the young man had come, it was best to first assess his background and ask a few questions.
"What have you studied?" Cai Yong asked. "What are your strengths?"
"I have a basic understanding of the Six Classics, but I particularly enjoy mathematics," Fei Qian replied, thanks to the knowledge of his predecessor. He remembered most of the Six Classics, though he couldn't delve into profound interpretations. But mathematics was a different story. After all, he had attended high school and university in his past life. No matter how brilliant the scholars of the Eastern Han Dynasty were, had they ever encountered matrices, calculus, or probability theory?
Fei Qian even considered mentioning that he knew a bit of "English," "Japanese," and other languages, but unfortunately, those skills were completely useless in the Eastern Han Dynasty.
Cai Yong was quite surprised, as mathematics was considered an advanced field of study during the Eastern Han Dynasty, not something the average person could master. The *Zhou Bi Suan Jing* (The Mathematical Classic of the Zhou Gnomon) had only been written two or three hundred years prior, and its text was often obscure and difficult to understand. Without strong imagination and deductive skills, one would be lost even after reading it. For example, the *Zhou Bi Suan Jing* contains a passage: "To find the distance to the sun, take the shadow on the ground as the base, the height of the gnomon as the perpendicular, square both, add them together, and take the square root to find the distance to the sun." This is the Pythagorean theorem. If one couldn't understand this, then mathematics was not for them.
There was another slightly more accessible text, the famous *Nine Chapters on the Mathematical Art*. However, at this time, the *Nine Chapters* had not yet been organized and annotated by Liu Hui, so it remained quite disorganized. Although it was more closely related to practical problems in daily life, it was still not an easy text to approach.
Cai Yong's interest was piqued. After all, few people in this era studied mathematics, and it was rare to find someone with similar interests. So, he casually posed a problem from the *Nine Chapters* to test Fei Qian: "There is a square city of unknown size. If you walk 20 paces north from the north gate, you will find a tree. If you walk 14 paces south from the south gate and then 1,775 paces west, you will see the same tree. What is the area of the city?"
Although the problem was short, it involved a lot of concepts. In addition to basic arithmetic, one needed to understand the theorem of similar triangles and how to solve a system of linear equations. In the *Nine Chapters*, this was considered a problem of moderate difficulty. Cai Yong had chosen it casually to see if Fei Qian truly understood mathematics.
But for Fei Qian, a problem of this level was no challenge at all. He asked Cai Yong for paper and a brush, drew a diagram, set up the equations, and quickly arrived at the answer.
Cai Yong, peering over his shoulder, could roughly guess that the diagram was a schematic, but what were those strange symbols—ABCD, 1234—scrawled on the paper? His curiosity was aroused, but he felt too embarrassed to ask.
Fei Qian considered showing off by posing the infamous "30-yuan math problem" from his past life, but he quickly dismissed the idea. That problem was inherently misleading, and while it might be fine to discuss in casual settings, if a great scholar like Cai Yong saw through it, it could reflect poorly on him. He might even earn a reputation for being "crafty," which could ruin his future prospects.
So, it was better to play it safe and act like a humble student. After all, everyone liked honest people, right?
After finishing his calculations, Fei Qian stood with his hands at his sides, assuming the posture of an obedient student.
Cai Yong carefully considered the situation and, after some hesitation, acknowledged Fei Qian's mathematical abilities. Finally, he said, "Very well, I will accept you as a nominal disciple. On the 3rd and 12th of each month, you may attend my lectures at the Imperial Academy. On the 5th and 20th, if you have questions, you may come here to ask. How does that sound?" A nominal disciple was still a disciple, so this wouldn't violate his earlier promise. As for whether Fei Qian would ever become a full disciple, that could be decided later. For now, Cai Yong could use Fei Qian's solution to the problem to ask his beloved daughter if she could understand it.
*****
A/N: The "30-yuan math problem" was essentially a trick question, and in ancient times, such cleverness, once exposed, could ruin one's reputation—especially in front of a great scholar.