Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
उभयत्रावगाढौ च लवणक्षीरसागरौ शाकद्वीपे तु वक्ष्यामि सप्त दिव्यान्महाचलान् //
ubhayatrāvagāḍhau ca lavaṇakṣīrasāgarau śākadvīpe tu vakṣyāmi sapta divyānmahācalān //
On both sides lie the oceans of salt and milk; and now, in regard to Śākadvīpa, I shall describe the seven divine great mountain ranges.
This verse is cosmographic rather than pralaya-focused: it maps the ordered structure of the world (dvīpas and surrounding oceans), implying a stable cosmic arrangement maintained across cycles.
Indirectly, it supports dharma through knowledge of sacred geography—useful for kings and householders in planning pilgrimages, patronage of rituals, and understanding the Purāṇic worldview that undergirds social and religious duties.
No direct Vāstu rule is stated, but such cosmography often provides the ritual-mental map for temple symbolism (cosmic oceans and mountains mirrored in temple layouts and consecration imagination).