The ancient academic qualifications were scholar, scholar, and Jinshi. Just like today's college students, master's degree and doctorate. Scholars can teach in private schools and be teachers. Caizi are the most knowledgeable, talented and famous among these people. There is a famous saying about their knowledge: A scholar can know the affairs of the world without going out. After reading the Book of Songs, one can speak, and after reading the Book of Changes, one can tell fortunes. That is, understanding astronomy. There is such a story: Emperor Qianlong went to the south of the Yangtze River and took a boat on the Grand Canal. Standing on the bow of the boat, a bamboo basket floated upstream. He was salvaged and asked Liu Yong next to him: "What is this?" Liu Yong replied: Bamboo basket. Asked again: What is it used for? He replied: Hold things. Why hold something? Can’t Sheng Nanbei? Liu Yong replied: The east belongs to wood and the west belongs to gold. They can be placed in baskets. The south belongs to fire and the north belongs to water, so they cannot be placed in a basket.