Yogic science gives as much importance to certain physical cleansing processes as it does to the puritiy of mind. Physical cleanliness is meant both internal and external, as without regular cleaning out of the system, not much can be expected from the exercises, and the aspirant would lack a safe base for the effective practice of Asana and Pranayama.

The textbooks of Hatha-Yoga mention “Shat-Karma”, the six cleansing acts, as the foundation for successful Yoga-Practice. These textbooks are known as “Yoga-Shastra”, amongst which the “Hatha-Yoga-Pradipika” by Yogi Svatmarama, the “Gheranda-Samhita” by the sage Gheranda and the “Shiva-Samhita” which originates directly from the mouth of Lord Shiva, who is the source of all Yoga, are the most widely used manuals on Hatha-Yoga.

Shat-Karma consists of the following practices:

1. Dhauti, the cleansing of the stomach by means of a cloth.
2. Vasti, the cleansing of the intestinal tracks by means of water and air.
3. Neti, the nasal cleansing by means of strings (Sutra-Neti) and saline water (Jala-Neti).
4. Nauli, the strengthening and massage of the abdominal organs by means of controlling and rolling the
    Nala  (abdominal muscle; musculus rectus abdominis).
5. Trataka, the purification of the eyes and the mind by means of steady conscious gazing.
6. Kapalabhati or Bhastrika, forceful inhaling and exhaling like the bellows of an iron monger.

The Yoga-Shastra mentions various other cleansing processes: two are of special importance, namely Kunjala or Gajakarani (elephant exercise) for cleansing out the stomach by means of water, and Shankha-Prakshalana (purification of the conch), the cleansing of the intestines by means of saline water.
These exercises keep the body immune to all kinds of diseases and make it glow with health.