Cleansing or purification processes of body and mind - Shatkarmas, also called shatkriyas or even kriyas - are well documented techniques in ancient Yoga texts.

The term shatkarma or shatkriya means ‘six actions’. The ancient rishis considered them as essential to the practice of Yoga: “In Yoga, control of the body starts with the cleansing processes known as the kriyas, the first step to eliminate poisonous substances accumulated in the system” (Sw. Vishnu-devananda).

Those cleansing processes are powerfully and profoundly purifying, acting at all levels of ‘being’. When the body is purified, then he is trained in Trataka (concentration). These six actions or Shatkarmas are the foundation of the meditative practices of Raja Yoga.

I found out this classification for the ‘six actions’:
1. Dhauti cleaning the stomach
2. Basti cleaning the colon
3. Neti cleaning the nasal passage
4. Nauli cleaning the abdominal organs
5. Kapalabati cleaning the respiratory organs
6. Trataka clearing the mind through gazing (externally or internally)

More:
Cleansing Processes (Shatkarmas)