At the beginning, pranayama is practised to destroy all obstacles and sins. This is arambha avastha, beginning or the first stage of pranayama. At this stage, during the practice the body of the yogi begins to perspire. When it perspires one should rub it well with the hands. Physical trembling also occurs, and the body sometimes jumps like a frog.
Ghata avastha is the second stage, which is acquired by constantly practising retention of breath. When perfect union takes place between prana and apana, manas and buddhi or jivatman and Paramatman without opposition, it is called ghata avastha. Once this is attained, only one-fourth of the period of time for practice is required by day and by evening one yama (three hours). Kevala kumbhaka should be practised once a day.
Drawing away completely the organs from the objects of the senses during cessation of breath is called pratyahara. This is described as: Whatever he sees with his eyes, let him consider as atman. Whatever he hears with his ears, let him consider as atman. Whatever he smells with his nose, let him consider as atman. Whatever he tastes with his tongue, let him consider as atman. Whatever the yogi touches with his skin, let him consider as atman. Then various wonderful powers are obtained by the yogi, such as clairvoyance, clairaudience, the power to levitate, ability to transport himself to great distances within a moment, great power of speech, ability to take up any form he likes, ability to become invisible and the wonder of transmuting iron into gold.
Then, should the wise yogi think that these powers are great obstacles in the attainment of yoga, he should never take delight or recourse to them. The yogins should not exercise these powers before any person whosoever. He should live in the world as an ordinary man in order to keep his powers concealed. His disciples would, without doubt, request him to show them his powers for the gratification of their desire. One who is actively engaged in ones (world-imposed) duties, forgets to practise yoga. So he should practise day and night nothing but yoga without forgetting the words of his guru. Thus he who is constantly engaged in yogic practices, passes the ghata state.
Then by such constant practice, the third state is gained. In the parichaya avastha, vayu or breath pierces the kundalini, along with agni through thought, and enters the sushumna along with prana. It reaches the high seat in the head, along with prana. When the practitioner acquires the power of action, kriya shakti, and pierces through the six chakras and reaches the secure condition of parichaya, he verily sees the threefold effects of karma.
Then let the yogi destroy the multitude of karmas by the pranava (Aum). Let him accomplish kaya-vyuha, a mystical process of taking various bodies, in order to exhaust all his previous karmas without the necessity of being reborn. At that time let the great yogi practise the five tattwa dharanas or forms of concentration by which command over the five elements is gained. In that way, fear of injuries by any one of them is removed.
Nishpatti avastha is the fourth stage of pranayama, this state of consummation is reached through graduated practice. Having destroyed all the seeds of karma, such a yogi feels neither hunger nor thirst, nor sleep nor swoon and drinks the nectar of immortality. He becomes absolutely independent, free from all diseases, decay and old age, and can move anywhere in the world. No longer in need of any yogic practice, he enjoys the bliss of samadhi. When the skilful tranquil yogi can drink the prana vayu by placing his tongue at the root of the palate, when he knows the laws of action of prana and apana, then he becomes entitled to liberation.
A yogic student will automatically experience all these avasthas one by one as he advances in his systematic, regular practices. An impatient student cannot experience any of these avasthas through occasional practices.