Matsya Purana — Solar–Lunar Motions
लोक आलोकने धातुर् निरालोकस्त्वलोकता लोकालोकौ तु संधत्ते यस्मात्सूर्यः परिभ्रमन् //
loka ālokane dhātur nirālokastvalokatā lokālokau tu saṃdhatte yasmātsūryaḥ paribhraman //
The dhātu (element) that makes the worlds visible is light; the condition of being without light is darkness. For this reason the Sun, as he revolves, joins together the realm of light and the realm beyond light (Lokāloka).
It does not describe Pralaya directly; it explains cosmic order—how light and darkness are defined and how the Sun’s movement functions as the connector between the illuminated worlds and the dark boundary-region called Lokāloka.
Indirectly, it frames dharma through cosmic regularity: just as the Sun maintains order by its circuit, a king/householder should sustain social order through disciplined, consistent conduct aligned with truth and clarity (āloka) rather than ignorance (alokatā).
While not a Vāstu rule, it supports ritual/temple orientation logic: Surya and illumination are central to auspicious directionality and daily rites (e.g., sun-facing alignments and timing), reflecting the Purāṇic view that light governs sacred space and sacred time.