Answer:
According to a book written during the reign of Tang Empress Wu, Fokan Ji (佛龕記, An Account of Buddhist Shrines) by Li Junxiu (李君修), a Buddhist monk named Lè Zūn (樂尊, which may also be pronounced Yuezun) had a vision of a thousand Buddhas bathed in golden light at the site in 366 AD, inspiring him to build a cave here.
Step-by-step explanation: