Skandapurana 7.18.89_146

7.18.89_146

From drawing in [the breath] just once, and from releasing it repeatedly, / this is designated as kumbhaka, from the holding of prāṇāyāma and the rest.
This vital breath (prāṇa) is the wind, the self in the body, the living […] / One should know its two forms: coarse and subtle everywhere.