Master Chang Sen Feng was an active Taoist master during the Tang Dynasty (660-780 AD). He was schooled in the Chai Tzan tradition, which he practiced, expanded and taught. His personal practice led him to explore techniques that favored the use of sexual energy as a source for internal alchemy. This text, his record of the practice, disappeared for over 700 years before it was rediscovered by Jie Yi Tze during the Ming Dynasty.