Matsya Purana — The Greatness of Prayaga: Manasa Tirtha
गङ्गायमुनयोर्मध्ये कर्षाग्निं यस्तु साधयेत् अहीनाङ्गो ह्यरोगश्च पञ्चेन्द्रियसमन्वितः //
gaṅgāyamunayormadhye karṣāgniṃ yastu sādhayet ahīnāṅgo hyarogaśca pañcendriyasamanvitaḥ //
Whoever performs the austerity called “karṣāgni” in the land between the Gaṅgā and the Yamunā becomes free from bodily defect and disease, and remains endowed with all five senses.
This verse does not discuss pralaya or cosmology; it is a phalaśruti passage stating the bodily and sensory benefits gained by performing a specific austerity (karṣāgni) in the Gaṅgā–Yamunā region.
It aligns with the householder ethic of undertaking regulated vows and austerities at tīrthas for purification and well-being; it presents disciplined tapas as a legitimate dhārmic means to maintain health, integrity of the body, and full functioning of the senses.
The significance is ritual rather than architectural: it highlights a named observance (karṣāgni) and locates its efficacy specifically in the sacred Gaṅgā–Yamunā doab, emphasizing place-based merit (tīrtha-prabhāva).