What is the relationship between Yuan Tiangang and Li in history?

The relationship between Li and Yuan Tiangang

Teacher and pupil: It is said that Yuan Tiangang lives near Panlong Mountain in Langzhou, and he is knowledgeable and has a good reputation. Li was so envious of his knowledge that he came from far away with money and became his apprentice. Together, they wrote the book Four Marbles, which was later proofread by Liu Bowen of the Ming Dynasty.

Friend's statement: Yuan Tiangang and Li are classmates and friends who study together. They often get together to discuss the knowledge of natural phenomena, principles and changes, and discuss ancient and modern things. It is said that Yuan Tiangang and Li are sitting back to back. One is responsible for writing and the other is responsible for drawing. The division of labor is wonderful.

Li and Yuan Tiangang were famous fortune tellers in Tang Dynasty, and they advocated Taoism. Their relationship is either mentoring, friendship or nothing, but later generations artificially linked them because of their similar experiences. The story of Li and Yuan Tiangang has spread to this day, and it is impossible to verify it.