Like metals purified over fire in the crucible, the slag of karma is removed by Pranayama and the mind is freed from contamination.

This and Kaya shuddhi are both brought about; the mind and the body are both rendered pure. There are two types of Pranayama - the one with Mantra and the other without it. Without Mantra, it can at best transform the body only, but with Mantra, it transforms the mind also. Two seconds long Purakam, four seconds long Rechakam, eight seconds long Kumbhakam - in this series. Pranayama has to be practised carefully for three months; later, the duration of Purakam, Rechakam and Kumbhakam can be doubled. When six months are spent in this steady practice, the activities of the senses are laid low.

If practised with faith and feeling, Pranayama will tame the agitations of the mind; otherwise, it becomes a mere physical exercise, improving only the physical health. Pure food,Brahmacharya, living in solitude, moderate speech - these conditions too have to be strictly observed. (P.Vah, p. 302)

The Prana, or vital air, the Sarira, which is its basis, the Shiras, which is the seat of the instruments of acquiring knowledge, the strength that is derived from food - all these are considered in Brihadaranyaka Upanishad. Hunger and thirst are qualities of the Prana; birth and death are characteristics of the body; grief and delusion are afflictions of the mind. (GV, p. 86)