Matsya Purana — The Greatness of Prayaga and Allied Tirthas
प्रभावात्सर्वतीर्थेभ्यः प्रभवत्यधिकं विभो दश तीर्थसहस्राणि तिस्रः कोट्यस्तथा पराः //
prabhāvātsarvatīrthebhyaḥ prabhavatyadhikaṃ vibho daśa tīrthasahasrāṇi tisraḥ koṭyastathā parāḥ //
O mighty one, by its spiritual potency it surpasses all other sacred fords (tīrthas): it yields merit greater than ten thousand tīrthas, and even beyond three crores besides.
It does not discuss pralaya directly; it focuses on tirtha-mahātmya—how a particular sacred place, by its inherent prabhāva (spiritual efficacy), grants exceptionally high merit compared to other pilgrimage sites.
It supports the dharmic duty of undertaking tīrtha-yātrā (pilgrimage) and performing meritorious acts; for kings and householders, such high-efficacy tirthas are presented as efficient means to accumulate punya and uphold religious life.
Architectural rules are not stated; the ritual takeaway is that some tirthas are believed to multiply the fruit of rites (bathing, offerings, vows) many-fold due to their prabhāva, exceeding the merit of visiting vast numbers of other sites.