Kumbhaka is of two kinds, viz., Sahita and Kevala. That which is coupled with inhalation and exhalation is termed Sahita. That which is devoid of these is called Kevala (alone). When you get mastery in Sahita, then you can attempt for this Kevala. When in due course of practice, the Kumbhaka subsists in many places without exhalation and inhalation, unconditioned by place, time and number -then that Kumbhaka is called absolute and pure (Kevala Kumbhaka), the fourth form of 'Regulation of breath'. Such powers as that of roaming about in space unseen, follow this last form of Pranayama. In Vasishtha Samhita it is said: "When after giving up inhalation and exhalation, one holds his breath with ease, it is absolute Kumbhaka (Kevala)." In this Pranayama the breath is suddenly stopped without Puraka and Rechaka. The student can retain his breath as long as he likes through this Kumbhaka. He attains the state of Raja Yoga. Through Kevala Kumbhaka, the knowledge of Kundalini arises. Kundalini is aroused and the Sushumna is free from all sorts of obstacles. He attains perfection in Hatha Yoga. You can practise this Kumbhaka three times a day. He who knows Pranayama and Kevala is the real Yogi. What can he not accomplish in the three worlds, who has acquired success in this Kevala Kumbhaka? Glory, glory to such exalted souls. This Kumbhaka cures all diseases and promotes longevity.