Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
सौमनं प्रथमं वर्षं धातकीखण्डमुच्यते धातकिनः स्मृतं तद्वै प्रथमं प्रथमस्य तु //
saumanaṃ prathamaṃ varṣaṃ dhātakīkhaṇḍamucyate dhātakinaḥ smṛtaṃ tadvai prathamaṃ prathamasya tu //
In the Dhātakīkhaṇḍa, the first varṣa (region) is called Saumana; and that is remembered as Dhātakina—the foremost division of that first section.
This verse is not about pralaya; it catalogs cosmic geography, naming the first regional division (varṣa) within Dhātakīkhaṇḍa as part of the Purāṇic world-structure.
Indirectly, it supports the Purāṇic ideal that rulers understand the sacred layout of the world (dvīpas/varṣas) for pilgrimage, ritual orientation, and maintaining dharmic order across regions.
No explicit Vāstu or temple rule is stated; the significance is ritual-geographic—naming regions used in Purāṇic mapping for tīrtha-travel, recitation contexts, and cosmological orientation.