Vijnana Bhairava Tantra
36: By stopping the openings with the weapon in the form of the hands, by which are blocked the eyes and thus by breaking open the bindu is perceived which on the development of one-pointedness gradually disappears in the ether of consciousness. Then in the centre of the ether of consciousness, the yogi is established in the highest spiritual state.
37: The yogi should meditate either in the heart or in dvadasanta on the bindu which is a subtle spark of fire resembling a tilaka produced by pressure on the dhama or teja (light existing in the eyes). By such practice the discursive thought (vikalpa) of the yogi disappears, and on its disappearance, the yogi is absorbed in the light of supreme consciousness.
38: One, who is adept in listening to the unstruck sound called anahat, which is uninterrupted like a rushing river masters the shabdabrahman, the form of Brahman as sound and attains the supreme state of Brahma.
39: O Bhairavi, by perfect recitation of pranava or the sacred syllable Aum and by contemplating over the void at the end of the protracted phase of it and by the most eminent energy of the void, the yogi attains the void.
40: The Yogi should contemplate over the previous condition of any letter whatsoever before its utterance and its final condition after its utterance as mere void. He will, then with the help of the power of the void, become of the nature and form of the void.