sankhyabhih paridrishto deergha-sukshmah."
Yoga Sutras-Ch. II-50
Pranayama is regarded lengthy or subtle according to its three components, the external, the internal and the steady; the retention processes are modified by the regulation of space, time and number.
When the breath is expired, it is Rechaka, the first kind of Pranayama. When the breath is drawn in, it is the second, termed Puraka. When it is suspended, it is the third kind, called Kumbhaka. Kumbhaka is retention of breath. Kumbhaka increases the period of life. It augments the inner spiritual force, vigour and vitality. If you retain the breath for one minute, this one minute is added to your span of life. Yogins by taking the breath to the Brahmarandhra at the top of the head and keeping it there, defeat the Lord of death, Yama, and conquer death. Chang Dev lived for one thousand and four hundred years through the practice of Kumbhaka. Each of these motions in Pranayama, viz., Rechaka, Puraka and Kumbhaka, is regulated by space, time and number. By space is meant the inside or outside of the body and the particular length or the breadth and also when the Prana is held in some particular part of the body. During expiration the distance to which breath is thrown outside varies in different individuals. The distance varies during inspiration also. The length of the breath varies in accordance with the pervading Tattva. The length of the breath is respectively 12, 16, 4, 8, 0 fingers' breadths according to the Tattvas-Prithvi, Apas, Tejas, Vayu and Akasa (earth, water, fire, air and ether). This is again external during exhalation and internal during inhalation.
Time is, the time of duration of each of these, which is generally counted by Matra, which corresponds to one second. Matra means a measure. By time is also meant how long the Prana should be fixed in a particular centre or part.
Number refers to the number of times the Pranayama is performed. The Yogic student should slowly take the number of Pranayamas to eighty at one sitting. He should have four sittings in the morning, afternoon, evening and midnight, or at 9 a.m., and should have thus 320 Pranayamas in all. The effect or fruit of Pranayama is Udghata or awakening of the sleeping Kundalini. The chief aim of Pranayama is to unite the Prana with the Apana and take the united Prana-Apana slowly upwards towards the head.
Kundalini is the source for all occult powers. The Pranayama is long or short according to the period of time it is practised. Just as water, thrown on a hot pan shrivels upon all sides as it is being dried up, so also air, moving in or out ceases its action by a strong effort of restraint (Kumbhaka) and stays within.
Vachaspati describes-"Measured by 36 Matras, is the first attempt (Udghata), which is mild. Twice that is the second, which is middling. Thrice that is the third, which is the intense. This is the Pranayama as measured by number."
The 'place' of exhalation lies within 12 Angulas (inches) of the tip of nose. This is to be ascertained through a piece of reed or cotton. The place of inhalation ranges from the head down to the soles of the feet. This is to be ascertained through a sensation similar to the touch of an ant. The place of Kumbhaka consists of the external and internal places of both exhalation and inhalation taken together, because the functions of the breath are capable of being held up at both these places. This is to be ascertained through the absence of the two indicatives noted above, in connection with exhalation and inhalation.
The specification of the three kinds of breath regulations, by all these three-time, space and number-is only optional. They are not to be understood as to be practised collectively, for in many Smritis we meet with passages, where the only specification mentioned with reference to the regulation of breath is that of time.
The fourth is restraining the Prana by directing it to external or internal object; "Bahyabhyantaravishayakshepi chaturthah" (Yoga Sutras: II-51).
The third kind of Pranayama that is described in Sutra 50 of the Yoga Sutras, is practised only till the first Udghata is marked. This fourth Pranayama is carried further. It concerns with the fixing of the Prana in the various lotuses (Padmas or Chakras) and taking it slowly, and slowly, step by step, and stage by stage to the last lotus in the head, where perfect Samadhi takes place. This is internal. Externally it takes into consideration the length of breath in accordance with the prevailing Tattva. Prana can be described either inside or outside.
By gradual mastery over the preliminary three kinds of Pranayama, the fourth kind comes in. In the third kind of Pranayama the sphere is not taken into consideration. The stoppage of the breath occurs with one single effort and is then measured by space, time and number and thus becomes Dirgha (long) and Sukshma (subtle). In the fourth variety, however the spheres of expiration and inspiration are ascertained. The different states are mastered by and by. The fourth variety is not practised all at once by a single effort like the third one. On the other hand, it reaches different states of perfection, as it is being done. After one stage is mastered, the next stage is taken up and practised. Then it goes in succession. The third is not preceded by measurements and is brought about by a single effort. The fourth is however preceded by the knowledge of the measurements, and is brought about by much effort. This is the only difference. The conditions of time, space and number are applicable to this kind of Pranayama also. Particular occult powers develop themselves at each stage of progress.