Matsya Purana — Cosmic Architecture of Sun–Moon and the ‘Houses of the Gods’
द्विगुणः सूर्यविस्ताराद् विस्तारः शशिनः स्मृतः त्रिगुणं मण्डलं चास्य वैपुल्याच्छशिनः स्मृतम् //
dviguṇaḥ sūryavistārād vistāraḥ śaśinaḥ smṛtaḥ triguṇaṃ maṇḍalaṃ cāsya vaipulyācchaśinaḥ smṛtam //
The Moon’s breadth is said to be twice the Sun’s breadth; and the Moon’s disc (maṇḍala) is remembered as threefold in extent, owing to the Moon’s greater spread.
This verse is not about Pralaya; it belongs to cosmological measurement, describing comparative dimensions of the Sun and Moon as part of the Purana’s world-model.
Indirectly, it supports calendrical and time-reckoning knowledge (Moon/Sun measures) that underlies royal administration and household ritual timing, though the verse itself is purely descriptive.
Ritually, Sun–Moon measures inform traditional luni-solar timekeeping used for selecting tithis and festival timings; there is no direct Vastu or temple-construction rule stated in this shloka.