Zhang Bo-Duan carefully composed the book Wu Zhen Pian (Understanding Reality) after trying three times to pass on his knowledge, and three times failing due to having chosen unsuitable people. In the postscript Zhang Boduan said
“In this book of mine, everything is made ready for you, the verses and songs have the firing process of the great elixir, and all the subtle directions. Those who have an affinity for this matter must have the bones of a transcendent, then when they read this book carefully and with wisdom it will inspire clarity. They can search the text to unravel the significant meaning of terms, there will be no need for personal oral transmission by my humble self. This book is in fact a bequest from Heaven, not my own presumption.”
The Fat Monk 