The Chinese yin-yang sexual practice (房中術) exits before Han-Dynasty (202-220 BC). It came from the ancient thought of Yin and Yang (陰陽) – a balanced status in everything. After Taoism is founded, the Taoists take the yin-yang sex as Taoist practice to gain their Taoist achievement: train the mind to return to void (練神還虛). During the envelopment of Taoism, there are two main paths: One practices yin-yang sex to get the Taoist achievement (e.g.養生派); the other gives up yin-yang sex but makes another practice to reach the final Taoist goal (e.g.上清派).
There is a parallel between Taoism and Lamaism (= Tibetan Buddhism). But:
1. The Yin-Yang sex is one path of Taoism. Some taoists do not see Yin-Yang sex as center of their practices; Further more, they have to give up sexuality to achieve taoist goals.
2. The taoists lay methods of Yin-Yang sex in the sun. They never lie to others there is no Yin-Yang sex in Taoism.
3. The Taoism shows its true face as Taoism. The Taoists neither tell others they are Buddhists nor insist Taoism is Buddhism.
And how about the Lamaism?
1. Lamas have to practice Tantric sex to become enlightened. In other words, the Tantric sex is the center practice of Lamaism.
2. Lamas never inform the beginner of their Tantric sex.
3. Lamas hide their true face and behave themselves as Buddhists. How could one practice Tantric sex and tell others it is Buddha’s teaching?
As a Buddhist, it is important to follow the teachings of Buddha. One who insists to be a Buddhist but practice Tantric sex every day, has to be called Lama.