Matsya Purana — The Greatness of Prayaga: Manasa Tirtha
अधःशिरास्तु यो ज्वालाम् ऊर्ध्वपादः पिबेन्नरः शतवर्षसहस्राणि स्वर्गलोके महीयते //
adhaḥśirāstu yo jvālām ūrdhvapādaḥ pibennaraḥ śatavarṣasahasrāṇi svargaloke mahīyate //
A man who, hanging with his head downward and his feet upward, “drinks” (endures) the blazing fire is honored in the heavenly world for a hundred thousand years.
This verse does not discuss Pralaya; it focuses on karmaphala—how extreme tapas is said to yield prolonged honor in Svarga.
Indirectly, it reinforces the Purāṇic ethic that disciplined self-restraint and religious observance produce merit; for kings/householders, the implied takeaway is to support dharma and regulated vows rather than imitate dangerous ascetic extremes.
No Vāstu or temple-architecture rule appears here; the ritual significance is the broader vrata/tapas framework where austerity is presented as a means to accrue religious merit (puṇya).