Matsya Purana — Solar Dynasty Prelude: Vivasvān–Saṃjñā–Chāyā
अज्ञातसमयो राजा इलः शरवणे पुरा स्त्रीत्वमाप विशन्न् एव वडबात्वं हयस्तदा //
ajñātasamayo rājā ilaḥ śaravaṇe purā strītvamāpa viśann eva vaḍabātvaṃ hayastadā //
Unaware of the sacred restriction of time and place, King Ila once entered the Śaravaṇa grove; and at that very moment he attained womanhood, while his horse then became a mare.
This verse does not address Pralaya; it belongs to a dynastic narrative illustrating how violating or unknowingly entering a restricted sacred space/time can trigger extraordinary consequences.
It underscores vigilance regarding dharmic boundaries—kings are expected to know and respect sacred prohibitions (kāla-deśa-niyama), since careless entry into restricted zones can bring personal and political disruption.
The ritual takeaway is the idea of a restricted sacred precinct (a place governed by specific rules); while not Vāstu-technical, it echoes Purāṇic emphasis on observing site-based prohibitions when entering consecrated or specially regulated areas.