Nauli in the context of "Hatha yoga"

Hatha yoga (/ˈhʌtə, ˈhɑːtə/; Sanskrit हठयोग, IAST: haṭhayoga) is a branch of yoga that uses physical techniques to try to preserve and channel vital force or energy. The Sanskrit word हठ haṭha literally means "force", alluding to a system of physical techniques. Some hatha yoga style techniques can be traced back at least to the 1st-century CE, in texts such as the Hindu Sanskrit epics and Buddhism's Pali canon. The oldest dated text so far found to describe hatha yoga, the 11th-century Amṛtasiddhi, comes from a tantric Buddhist milieu. The oldest texts to use the terminology of hatha are also Vajrayana Buddhist. Hindu hatha yoga texts appear from the 11th century onward.

Some of the early hatha yoga texts (11th-13th c.) describe methods to raise and conserve bindu (vital force, that is, semen, and in women rajas – menstrual fluid). This was seen as the physical essence of life that was constantly dripping down from the head and being lost. Two early hatha yoga techniques sought to either physically reverse this process of dripping by using gravity to trap the bindhu in inverted postures like viparītakaraṇī, or force bindu upwards through the central channel by directing the breath flow into the centre channel using mudras (yogic seals, not to be confused with hand mudras, which are gestures).