Swami Vivekananda in his "Raja Yoga - Conquering the Internal Nature", Advaita Ashrama, Calcutta, 1998, speaks of this birth that is regarded highly by all the saints.
"The human body is the greatest body in the universe, and a human being is the greatest being. Even the Devas (Gods) will have to come down again and again to attain salvation through a human body. This human birth is the greatest we can have."
Man alone attains perfection, not even the Devas says the Swami. The human birth is necessary to free oneself. The body is the best instrument we have to achieve this purpose. We are moved by Prana to inhale and exhale he says. How do we retain this prana in us? The means is by Yoga. "The form of yoga known as Raja Yoga is based on the aphorisms of Patanjali. The science of Raja Yoga proposes to give us a means of observing the internal states."
"First, the nerves are to be purified, then comes the power to practice Pranayama. Stopping the right nostril with the thumb, through the left nostril fill in air, according to capacity; then, without any interval, throw the air out through the right nostril, closing the left. Again inhaling through the right nostril eject through the left, according to capacity; practicing this three or four times at four hours of the day, before dawn, during midday, in the evening, and at midnight, in 15 days or a month purity of the nerves is attained; then begins Pranayama."
The transformation comes with Pranayama and the control of the motion of the lungs, says Swami Vivekananda.
"Nerve currents will have to be displaced and given a new channel. New sorts of vibration will begin, and the whole constitution will be remodeled, as it were. But the main part of the activity will lie along the spinal column, so that the one thing necessary for the posture is to hold the spinal column free, sitting erect, holding the three parts - the chest, neck, and head - in a straight line. Let the whole weight of the body be supported by the ribs, and then you have a natural easy posture, with the spine straight."
Swami Vivekananda reminds us the aim, the end, the goal of all yogic training is the liberation of the soul and absolute control of nature. He says "The world is ready to give up its secrets if we only know how to knock."
Swami Vivekananda says "The whole world is in motion because of Prana. The most obvious manifestation of Prana is the breath. To reach the subtle we must take the help of the gross, and so, slowly travel towards the most subtle until we gain our point. To get into the subtle perception, we need to begin with the grosser perception. From the external, we move to the internal. Use the breath to slowly enter the body and find out the subtle forces at work in the body."
Korakar in his "Chandraregai 200", mentions the means of retaining the breath within and subduing the mind at the same time, making this body God's dwelling.
பான்மையுறப் பதினெண்பேர் நாதாக்கள் தாம்பாலிதங்களான தொறு ஞான சூட்சம்
மேன்மையுட னோதிடுவேன் வாசி கூட்டி
முக்கோணம் அதனுள்ளே வட்டம் சோதி
ஆன்மமுடன் நீ பார்த்து அசையா துற்றால்
ஆதாரமாக மனம் அசையா துய்யும்
வான் மதியும் ரவியடங்கும் வட்டத் துள்ளே
வாசிவெளி யாகாது ஞான வீடே 192
Its translation,
"I shall share a divine secret of the 18 Nattakal,
Inhaling, bringing your soul or Atma to witness or look into the circular Jhoti within the triangle,
the mind tends to settle, the moon and sun set into the circle,
the breath is stalled within, leading to the kingdom of Gnana."
Kalanginathar also speaks of this triangle in his "Upadesa Gnanam 34".
ஆவியென்ற பிராணமது புருவமீதுஅடங்கினால் மறுபிறவி யுண்டாம் பாரு
ஆவியென்ற பிராணனது முக்கோணத்தில்
அடங்கினால் மறுபிறவி யில்லை யில்லை 21
"When the Prana settles in at the Agnai,
there shall be another birth,
But when it settles in the triangle,
there is no further birth."