In the Taoist sex classic, the eponymous Su Nu, a goddess-courtesan, instructs the mythical Yellow Emperor on the best ways to enjoy life and sex. One should calm the mind, harmonise the emotions and concentrate the spirit before intercourse, she counsels. Then, having settled the body and composed one’s thoughts, ‘penetrate deeply and move slowly’. The male should avoid climax to stave off the inevitable bout of post-coital depression, however. ‘When ching [semen] is emitted, the whole body feels weary,’ she explains. ‘One suffers buzzing in the ears and drowsiness in the eyes; the throat is parched and the joints heavy. Although there is brief pleasure, in the end there is discomfort.’ By withholding semen, the emperor would not only stay healthy, but extend his life indefinitely. ‘Nine acts without emission, and one will enjoy unlimited longevity. Ten acts without emission, and one attains the realm of the immortals.’ Further, Su Nu says, he should have intercourse frequently, with as many partners as possible, while focusing on the pleasure of the female. In the end, the Yellow Emperor seems to have learned his lessons well. It was said he kept a harem of 1,200 women entertained, and achieved immortality.