Śivasaṃhitā 3.89

The two sandhyās — the twilights of dawn and dusk — are the moments when the kākacañcvā (crow’s beak) practice is most effective, according to tantric yoga’s temporal logic. At those transitional instants, prāṇa flow between iḍā and piṅgalā naturally changes, and the suṣumnā channel briefly opens. Prāṇa ingested through the crow’s beak at that precise moment finds the central channel momentarily permeable.

«It cannot be practiced by everyone» (na śakyate sarvaloke): one of the text’s most honest declarations about tantric yoga’s elitist nature. The Śivasaṃhitā is not a popular manual: it is a transmission text for qualified disciples. Qualification (adhikāra) is not of social class or gender — but of inner preparation: nāḍīs sufficiently purified, mind sufficiently trained, body sufficiently stabilized by preliminary practices.

Only the medhāvin (the wise) attains success: medhā designates the intelligence that retains, assimilates, converts experience into permanent knowledge. Not the intellectual brilliance impressed by concepts but the depth that converts practice into transformation. It is the intelligence of the heart as much as the mind — the quality medieval masters recognized in the apt disciple before transmitting the most advanced techniques.