Śivasaṃhitā 5.94

Physical immortality (kāya-siddhi) was not metaphor for the tantrikas who authored this text. The promise of an indestructible body, harder than diamond (vajra), reflected the conviction that correct practice could reverse cellular degeneration processes through proper prāṇa circulation and bindu sublimation.

Sahasra is a thousand, indicating a mythic number of fullness and vastness rather than an arithmetic one. Vajra is both diamond and thunderbolt, symbol of unbreakable consciousness in Vajrayāna tantrism. The hardness of the vajra-deha (diamond-body) alludes not only to physical resistance but to the mind’s impermeability to external disturbances.

Gorakṣanātha’s Nātha tradition developed specific alchemical practices (rasāyana) to achieve this vajra-deha, complementing yoga with ingestion of mineral and herbal preparations. The Śiva-saṃhitā inherits this doctrine and grounds it in cakra meditation as a more accessible method than external alchemy, achieving the same transformation from within.