Of course, the books on vassal studies are mainly Confucian classics. Emperor Kangxi had many teachers. For example, the teacher of the Crown Prince is Tang Bin, a college student, and Xu is also one of the teachers who have taught Kangxi children for a long time. Emperor Kangxi personally taught the princes all aspects of knowledge, from learning to getting along with others. Later, Yong Zhengdi compiled these contents into Courtyard Mottoes.