Matsya Purana — Cosmic Creation: Emergence of the Great Elements and the Navel-Lotus
ईषत्संक्षोभयामास सो ऽर्णवं सलिलाश्रयः अनन्तरोर्मिभिः सूक्ष्मम् अथ छिद्रमभूत्पुरा //
īṣatsaṃkṣobhayāmāsa so 'rṇavaṃ salilāśrayaḥ anantarormibhiḥ sūkṣmam atha chidramabhūtpurā //
Then that One who dwells in the waters gently stirred the ocean; and by the ceaseless succession of subtle waves, a minute opening (a small fissure) that had existed from before became manifest.
It portrays Pralaya as beginning with subtle, almost imperceptible disturbances in the cosmic ocean—small signs (minute waves and a tiny fissure/opening) preceding the larger cataclysm.
Indirectly, it supports the Matsya Purana’s ethic of vigilance: wise rulers/householders should heed small omens and early disturbances, acting with foresight rather than waiting for crises to become overwhelming.
No direct Vāstu or ritual rule is stated; however, the imagery of a “chidra” (opening/fissure) aligns with later Vāstu concerns about defects (chidra-doṣa) and the importance of detecting subtle faults early.