Matsya Purana — Solar–Lunar Motions
तिस्रः कोट्यस्तु सम्पूर्णा विषुवस्यापि मण्डलम् तथा शतसहस्राणि विंशत्येकाधिकानि तु //
tisraḥ koṭyastu sampūrṇā viṣuvasyāpi maṇḍalam tathā śatasahasrāṇi viṃśatyekādhikāni tu //
The circular sphere of the viṣuva line (viṣuva-maṇḍala) measures a full three koṭis; and in addition there are one hundred thousand plus twenty-one more.
This verse is not describing pralaya directly; it gives a cosmological measurement—quantifying the viṣuva-maṇḍala (equinoctial circle)—which belongs to the Purana’s astronomical and world-structure exposition.
Indirectly: kings and householders relied on calendrical and astronomical reckoning (equinox-related calculations) for timing rites, donations, and state rituals; this verse supplies the Purana’s cosmographic framework used to ground such time-keeping traditions.
Ritually, equinox-based understanding supports selecting auspicious times (kāla) for yajñas and consecrations; architecturally, it can inform orientation concepts (east–west alignment) though the verse itself primarily states a numerical measure of the cosmic circle.