Śivasaṃhitā 3.86

Sarasa (nourishing, full of juice, of substance) qualifies the air the yogin «drinks» (pibet): not ordinary air but prāṇavāyu impregnated with the qualities that the practitioner’s meditative state confers upon it. The wise one (sudhī) who practices pratyahaṃ (daily, each day) with the correct method (vidhina) establishes the regularity that transformation requires. One day may be missed; the accumulation of omissions is regression.

The connection between «drinking nourishing air» and siddhasana reveals the Śivasaṃhitā’s integrated vision: the posture is not an indifferent container for respiratory practice but its co-producer. Siddhasana, with its heels pressing the energetic points of the perineum and pubis, creates the pressure base directing prāṇa toward the subtle channels with an efficacy that no other posture equals for deep prāṇāyāma practice.

The kṣipra yoga siddhi — the rapid consummation of yoga — promised to whoever combines siddhasana with breath regulation is the text’s most pragmatic pedagogical promise. Not years of dispersed ascetic practice but the precise combination of posture + technique + regularity. The Śivasaṃhitā proposes that the path’s efficiency is as much a function of tool quality as of practitioner diligence.