Śivasaṃhitā 4.86

The lunar-solar binary cosmology structuring the practice of advanced Vajrolī finds here its most concise formulation. The bindu — white, cold, descending, associated with the mind (manas) — corresponds to the moon; the rajas — red, warm, ascending, associated with digestive fire (agni) — corresponds to the sun. This duality is the corporeal projection of the cosmic duality Śiva-Śakti, Puruṣa-Prakṛti, consciousness-energy.

Vidhumaya — ‘composed of moon, essentially lunar’ — uses vidhu (moon, the one that varies, from the root vidhav-, to vary, to change), emphasizing the changing nature of the moon as a reflection of the changing state of the mind. Sūryamaya — ‘composed of sun, essentially solar’ — describes rajas as the expansive, radiant, and active energy that transforms. The union of these two principles within the body (svaśarīre) is the cosmic copulation realized internally.

This doctrine connects with the most classical haṭhayoga: ha = sun = prāṇa, ṭha = moon = apāna; hatha yoga is literally ‘the yoga of the union of sun and moon’. Vajrolī carries this union to the densest level of the material body, using reproductive fluids as the most concentrated vehicles of solar and lunar energy. The physical practice is the support for subtle alchemy: without physical union, the energetic union cannot occur at the plane where it is most transformative.