"The illusory Samsaric Vasana, that has arisen through the practice of many lives, never perishes except through the practice of Yoga for a long time. It is not possible on the part of one to control the mind by sitting up again and again except through the approved means" (Muktikopanishad).
"How could Jnana, capable of giving Moksha, arise certainly without Yoga? And even Yoga becomes powerless in securing Moksha when it is devoid of Jnana. So the aspirant after emancipation should practise (firmly) both Yoga and Jnana" (Yogatattva Upanishad).
"Tatah kshiyate prakasavaranam-Thence the covering of the light is destroyed" (Yoga Sutras-II-52). Tamas and Rajas constitute the covering or veil. This veil is removed by the practice of Pranayama. After the veil is removed, the real nature of the soul is realised. The Chitta is by itself made up of the Sattvic particles, but it is enveloped by Rajas and Tamas, just as the fire is enveloped by smoke. There is no purificatory action greater than Pranayama. Pranayama gives purity and the light of knowledge shines. The Karma of the Yogi, which covers up the discriminative knowledge, is destroyed as he practises Pranayama. By the magic panorama of desire, the essence which is luminous by nature is covered up and the Jiva or individual soul is directed towards vice. This Karma of the Yogi which covers up the Light and binds him to repeated births, becomes attenuated by the practice of Pranayama every moment and is destroyed eventually. The afflictions and sins constitute the cover according to Vachaspati.
Manu says: "Let the defects be burnt up by Pranayama." Vishnu Purana speaks of Pranayama as an accessory to Yoga: "He who wants the air known as Prana by practice is said to have secured Pranayama."
"Dharanasu cha yogayata manasah-The mind becomes fit for concentration" (Yoga Sutras, II-53). You will be able to concentrate the mind nicely after this veil of light has been removed. The mind will be quite steady like the flame in a windless place as the disturbing energy has been removed. The word Pranayama is sometimes used collectively for inhalation, retention and exhalation of breath and sometimes for each of these severally. When the Prana Vayu moves in the Akasa-Tattva, the breathing will be lessened. At this time it will be easy to stop the breath. The velocity of the mind will be slowly lessened by Pranayama. It will induce Vairagya.
If you can suspend one inch or one digit of breath inside, you will obtain the powers of foretelling; if you can suspend two inches within, you will get the power of thought-reading; for suspending the breath for three inches, levitation; for four inches, psychometry, clairaudience, etc.; for five inches, moving about unseen by anybody in the world; for six inches, the power of 'Kaya Siddhi'; for seven inches, entering the body of another man (Parakaya Pravesa); for eight inches, the power to remain always young; for nine inches, the power to make Devatas to work as your servants; for ten inches, Anima, Mahima and other Siddhis; for eleven inches, you will attain oneness with Paramatman. When through great practice the Yogi can perform Kumbhaka for full three hours, then he can balance himself on his thumb. He undoubtedly attains all kinds of Siddhis. Just as fire destroys the fuel, so also Pranayama destroys the bundles of sins. Pratyahara makes the mind calm. Dharana steadies the mind. Dhyana makes one forget the body and the world. Samadhi brings infinite Bliss, Knowledge, Peace and Liberation.
During Yogic Samadhi, the flame of the Yogagni (fire of Yoga) extending from navel to the head melts the Amrita in the Brahmarandhra. The Yogi drinks this with joy and ecstasy. He can remain without food and drink for months by drinking this Yogic nectar alone.
The body becomes lean, strong and healthy. Too much fat is reduced. There is lustre in the face. Eyes sparkle like a diamond. The practitioner becomes very handsome. Voice becomes sweet and melodious. The inner Anahata sounds are distinctly heard. The student is free from all sorts of diseases. He gets established in Brahmacharya. Semen gets firm and steady. The Jatharagni (gastric fire) is augmented. The student becomes so perfect in Brahmacharya that his mind will not be shaken even if a fairy tries to embrace him. Appetite becomes keen. Nadis are purified. The Vikshepa is removed and the mind becomes one-pointed. Rajas and Tamas are destroyed. The mind is prepared for Dharana and Dhyana. The excretions become scanty. Steady practice arouses inner spiritual light, happiness and peace of mind. It makes him an Urdhvareto-Yogi. Advanced students only will get all the other Siddhis mentioned above.
The mind of a man can be made to transcend ordinary experience and exist on plane higher than that of reason known as superconscious state of concentration and get beyond the limit of concentration. He comes face to face with facts which ordinary consciousness cannot comprehend. This ought to be achieved by proper training and manipulation of the subtle forces of the body so as to cause them to give, as it were, an upward push to the mind into the higher regions. When the mind is so raised into the superconscious state of perception, it begins to act from there and experiences higher facts and higher knowledge. Such is the ultimate object of Yoga, which can be achieved by the practice of Pranayama. The control of the vibratory Prana means to a Yogi, the kindling of the fire of supreme knowledge, the realisation of the Self.