Matsya Purana — Nārāyaṇa as Haṃsa in the Cosmic Ocean: Vedic Yajña-Puruṣa and Mārkaṇḍeya’s Vi...
*मार्कण्डेय उवाच इच्छेयं तत्त्वतो मायाम् इमां ज्ञातुं तवानघ यदेकार्णवमध्यस्थः शेषे त्वं बालरूपवान् //
*mārkaṇḍeya uvāca iccheyaṃ tattvato māyām imāṃ jñātuṃ tavānagha yadekārṇavamadhyasthaḥ śeṣe tvaṃ bālarūpavān //
Mārkaṇḍeya said: O sinless one, I wish to know, in its true reality, this māyā of yours—by which, in the midst of the single cosmic ocean, you abide upon Śeṣa in the form of a child.
It points to the Pralaya setting: the universe reduced to the single cosmic ocean (ekārṇava), while the Lord remains present—resting on Śeṣa—showing that dissolution does not negate the sustaining divine reality.
Indirectly, it frames dharma as grounded in discerning reality (tattvataḥ): rulers and householders are urged in the Purāṇic ethos to seek true understanding beyond appearances, cultivating humility and devotion rather than pride in transient worldly order.
No direct Vāstu or ritual rule is stated, but the imagery (the Lord on Śeṣa in the cosmic waters) is iconographically significant and can guide devotional visualization and temple imagery associated with Pralaya and Viṣṇu-Ananta motifs.