NĀḌĪCAKRA The ten nāḍīs where the yogī in meditation retains the five prāṇas form the nāḍicakra. At the bottom of the nābhi (nābhīkanda) innumerable nāḍīs or nerves originate or sprout up. 72,000 such nāḍīs exist at the centre of the nābhi (navel). The whole body is filled with these nāḍīs spread out in parallel and horizontal positions, and they exist in the form of circles entwined with one another. Ten nāḍīs are prominent amongst them, i.e. Iḍā, Piṅgalā, Suṣumnā, Gāndhārī, Hastijihvā, Pṛthā, Yaśā, Alambuṣā, Kuhā and Śaṅkhinī. Any defect or harm caused to any one of these ten nāḍīs may lead even to death. There are ten Vāyus (winds) in the body. The five Prāṇas called Prāṇa, Apāna, Samāna. Udāna and Vyāna, and the five Vāyus called Nāga, Kūrma, Kṛkala, Devadatta and Dhanañjaya together constitute the ten Vāyus. Prāṇa is the most important Vāyu. This vāyu does the emptying as well as the refilling of the other nine vāyus and thus sustains life. The prāṇavāyu has its existence ever in the chest of living beings and fills the body with air through breathing in, out, coughing etc. It depends on life and it is called Prāṇavāyu as it moves or travels with life. Apāna leads vāyu downwards. It is Apāna which directs man's food downwards. Also it keeps in its fold urine and semen. This vāyu is called Apāna as its function is adhonayana (leading downwards) as mentioned above. Samānavāyu conveys to the different parts in the body in equal manner the things which living beings eat, drink and smell as also blood, bile, phlegm and vāta. Udāna causes the shivering of lips, flushing of face and eyes and excitement of joints etc. Vyāna causes the limbs to be closed and stretched, and it excites diseases. Nāga exists in nausea, Kūrma in the bulging of the eyes Kṛkala in food, Devadatta in yawning and Dhanañjaya in sound. Dhanañjaya does not quit the body even after death. Life, Prāṇa, travels through the nāḍīcakra depending on ten different courses, i.e. Saṅkrānti, Viṣuva, Ahar, Rātri, the two ayanas (Dakṣiṇa and Uttara), Adhivāsa Ṛṇa, Ūnarātra and Dhana. Ūnarātra means hiccough, Ṛṇa cough, Dhana breathing and Adhivāsa yawning. Of the two ayanas, Uttara and Dakṣiṇa, the former is the course towards the left and the latter towards the right and Viṣuva is the centre between the two. Saṅkrānti is the change of position of Viṣuva. On he left side of the human body is the nāḍī called Iḍā, on the right side Piṅgalā and between the two Suṣumnā. The prāṇa above these three nāḍīs is Ahar i.e. day and that below is Apāna, i.e. night. Thus every vāyu assumes ten different forms. There are various kinds of prāṇāyāma (control of breaths). Prāṇāyāma practised with the prāṇa contained in the centre of the body is called Candragrahaṇa; that which supersedes physical principles is called Sūryagrahaṇa. To fill the stomach with as much of vāyu as is desired is Pūrakaprāṇāyāma. To remain like a full pot, all breathing stopped, (Pot completely filled) having closed all the openings--‘doors’--of the body is Kumbhaka. The yogī practising Kumbhaka should direct the vāyu upwards in one breath, and that practice is called Recaka. He who does it should be conversant with the yoga of inhalation. Erudite people call it Japa, because when it is practised Śiva resident in one's own body awakes within. Śiva, the King of yogins, chants the mantra (japa) 21,6000 times within the course of one day and one night. The soul chants the mantra-- Gāyatrī--of which Brahmā, Viṣṇu and Śiva are the presiding deities, and that is called Ajapa. He who chants Ajapa will have no future births. Prāṇāyāma should be followed by Kuṇḍalinīyoga, Kuṇḍalinī meaning primordial force. The force is a compound of Sun, fire and Moon and its seat is the heart, where it exists in the form of a sprout. Since creation is dependent upon this force power for creation should be invoked on it. The yogin should picture in his mind that nectar flows out of Kuṇḍalinī. He should also realise that the soul within the body possesses form while pure soul is formless. He should address this soul as ‘Haṁsa Haṁsa’. Haṁsa means Śiva. Śiva exists and functions inside and outside the body just as oil is in the gingelly seed and fragrance in flower. Soul possessing form is of five kinds. Accordingly Brahmā's seat is the heart, Viṣṇu's the neck, Rudra's, the centre of the throat; Maheśvara's the forehead; and Śiva's, the tip of the prāṇa. Soul without form is just contrary to the above. Its place is where the prāṇa ends. By prāṇāyāma the formless soul may be experienced.
[Agni Purāṇa, Chapter 214] .