Matsya Purana — The Greatness of Prayaga: Manasa Tirtha
गोभूहिरण्यदानेन यत्फलं प्राप्नुयान्नरः स तत्फलमवाप्नोति तत्तीर्थं स्मरते पुनः //
gobhūhiraṇyadānena yatphalaṃ prāpnuyānnaraḥ sa tatphalamavāpnoti tattīrthaṃ smarate punaḥ //
Whatever merit a person would obtain by gifting cows, land, and gold—he attains that very merit again simply by remembering that sacred tīrtha.
This verse does not address pralaya directly; it teaches a dharmic principle that remembrance of a sacred tīrtha can yield merit comparable to major donations.
It supports household and royal dharma by valuing dāna (cow, land, gold) while also affirming that mental devotion—remembering tīrthas—can generate comparable puṇya, especially when one cannot physically perform large gifts.
No vastu/temple-building rule is stated; the ritual takeaway is tīrtha-smaraṇa as a recognized merit-producing practice, placed alongside high-value dānas.