Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
शाल्मलस्य तु विस्ताराद् द्विगुणस्तस्य विस्तरः तस्मिन्द्वीपे तु विज्ञेयौ पर्वतौ द्वौ समाहितौ //
śālmalasya tu vistārād dviguṇastasya vistaraḥ tasmindvīpe tu vijñeyau parvatau dvau samāhitau //
But that dvīpa’s extent is said to be twice the breadth of Śālmaladvīpa; and within that dvīpa, two mountains are to be understood as situated together.
This verse does not describe Pralaya; it belongs to the cosmographic mapping of dvīpas, giving comparative measurements and noting mountains within an island-continent.
Directly it does not prescribe dharma; indirectly, such cosmography frames the Purana’s worldview used in ritual calendars, pilgrimage ideals, and the king’s role as protector of the ordered cosmos.
No explicit Vāstu or temple rule is stated; the significance is geographic-cosmological—mountains and dvīpa-measures often function as the sacred backdrop for Purāṇic ritual imagination and pilgrimage cosmology.