Taoist Ge Hong has a book "Bao Pu Zi", which is the earliest Taoist content in existing books. Ge Hong put forward the idea of Nine Secrets for the first time in this book.
Daoism is China's ancient works about tricks, and it is also the first secret among the three treasures of Qimen, Liu Ren and Taiyi. It is the first of the three types and the most reasonable method.