Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
लोकविस्तारमात्रं तु पृथिव्यर्धं तु बाह्यतः प्रतिच्छिन्नं समन्तात्तु उदकेनावृतं महत् //
lokavistāramātraṃ tu pṛthivyardhaṃ tu bāhyataḥ praticchinnaṃ samantāttu udakenāvṛtaṃ mahat //
The Earth’s outer half, extending only as far as the world’s breadth, is cut off on all sides and covered over by the vast waters.
It presents a cosmographic image in which the inhabited earth is bordered and enclosed by immense waters—an idea that also supports Pralaya imagery where waters dominate and envelop the world.
Indirectly, it grounds dharma in a cosmic order: rulers and householders are expected to act with awareness of the world’s structure and limits, fostering humility and restraint rather than limitless expansion.
No direct Vastu or ritual rule is stated, but the motif of “encirclement by waters” aligns with sacred planning symbolism (protective boundaries, circumambulation logic, and water as a purifying perimeter in temple and settlement layouts).