Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
शाल्मलान्तेषु विज्ञेयं द्वीपेषु त्रिषु सर्वतः व्याख्यातः शाल्मलान्तानां द्वीपानां तु विधिः शुभः //
śālmalānteṣu vijñeyaṃ dvīpeṣu triṣu sarvataḥ vyākhyātaḥ śālmalāntānāṃ dvīpānāṃ tu vidhiḥ śubhaḥ //
Thus, in every respect, what is to be understood concerning the three Śālmalānta islands has been explained; indeed, the auspicious ordinance and account of the Śālmalānta dvīpas has been set forth.
This verse is not a Pralaya passage; it is a concluding summary that the account of the Śālmalānta dvīpas (islands in Purāṇic cosmography) has been fully explained.
Indirectly, it supports the Purāṇic ideal that rulers and householders should know sacred geography and cosmology as part of dharmic learning (śāstra-jñāna), but it does not prescribe a specific duty here.
No direct Vāstu or ritual procedure is stated; the word "vidhi" here functions as an 'ordered account' of the dvīpas rather than a temple-building rule.