In the Yogasystems it is step 4 of the Ashtanga-Yoga. One goal is here to harmonize the five vayus by harmonizing the prana and to transform the forces of the Prana-Kundalini, which has also effects on the astral body with its emotions.
Patanjali discusses his specific approach to pranayama in verses 2.49 through 2.51 of his Yoga Sutras, and he devotes verses 2.52 and 2.53 to explaining the benefits of the practice.
Step 4 of Ashtanga-Yoga is also step 8 of the universal path. At this step the dark prana-maya-kosha - forces ( svadisthana-chakra with the Prana-Kundalini) are cleaned and refined.
To master the Prana and for Nadi Suddhi (purification of Nadis) traditionally different methods are used and combined:
* Kumbhaka - stopping breath while practicing pranayama (3 types: Bahya Kumbhaka - ie after complete exhalation, Antara Kumbhaka - i.e. after complete inhalation, Kevala Kumbhaka - rhytmic but very shallow breathing method)
* Nirmanu Pranayama - Alternating breath without Bija - Mantras
* Anuloma - alternate breathing with mantra, also known as Nadi Shodhana
* Bhastrika - Bellows - breath of Kundalini Yoga (Agni Prasana)
* Kapalabhati - shining skull, a Shatkriya - cleaning technique
* Shitkari- cooling respiration - mouth-guided technique without curling the tongue
* asceticism (discipline of the vital through will)
* Breathing exercises and breathing meditation
* Qigong - Circulation exercises - also with syllables like Ching et ..
* Special mantras (starting with 'OM') or quabbalistic formulas
* Exercises for cleaning the sushumna - for example Om kleem kleem kreem kreem namaha.
The Gheranda Samhita mentions another 10 methods of pranayama.
Vishnu's Matsya-avatar predicts the flood, and Satyavrata Manu flees with his family, many creatures and seeds in a ship.
The demon Hayagriva (also called 'ajnana' : ignorance) acts as a flood-maker and opponent of Vishnu, who must be destroyed by Matsya, who eventually throws himself at him and kills him.(U.Path 7)
This story is equivalent to noah's deluge.