“The Art of the bedroom constitutes the climax of human emotions and encompasses the totality of Tao. Therefore, the ancient sages disciplined their external pleasures, in order to control their inner passions. They established detailed rules governing sexual intercourse. If a man cultivates his sexual potency, he will feel at peace and attain longevity. But if a man abandons himself to sexual pleasure without regard for the rules set forth in the ancient texts, he will soon fall ill and gravely injure his life ”. 

– A Commentary from Pien Chang’s ‘Dynastic History’ of the Later Han Period.