Matsya Purana — Solar–Lunar Motions
विष्कम्भान्मण्डलाच्चैव भास्कराद्द्विगुणः शशी अतः पृथिव्या वक्ष्यामि प्रमाणं योजनैः पुनः //
viṣkambhānmaṇḍalāccaiva bhāskarāddviguṇaḥ śaśī ataḥ pṛthivyā vakṣyāmi pramāṇaṃ yojanaiḥ punaḥ //
In diameter and in its circular extent, the Moon is said to be twice that of the Sun. Therefore, I shall now again describe the measure of the Earth in yojanas.
This verse is not about pralaya; it belongs to cosmographical measurement, stating a proportional relationship between the Moon and the Sun and transitioning to the Earth’s dimensions.
Indirectly, it supports the Purāṇic ideal that rulers and householders should understand sacred cosmology and traditional units (like yojanas) for calendrical, ritual, and administrative reckoning.
No direct Vāstu rule is stated, but such cosmological proportions inform ritual timing and symbolic temple cosmology where the Sun–Moon–Earth order is reflected in sacred planning and calendrical rites.