Matsya Purana — Description of Gomedaka and Puṣkara Dvīpas; the Lokāloka Boundary; Ocean Tide...
आरोग्यायुःप्रमाणाभ्यां द्विगुणं द्विगुणं ततः द्वीपेषु तेषु सर्वेषु यथोक्तं वर्षकेषु च //
ārogyāyuḥpramāṇābhyāṃ dviguṇaṃ dviguṇaṃ tataḥ dvīpeṣu teṣu sarveṣu yathoktaṃ varṣakeṣu ca //
In health, lifespan, and bodily measure, it is doubled and then doubled again, in all those continents (dvīpas) and likewise in the regions (varṣas) that have been described.
It does not describe Pralaya directly; it belongs to cosmography, stating a graded increase (doubling) of health, lifespan, and bodily measure across the dvīpas and their varṣas.
Indirectly, it frames human conditions (health and longevity) as varying by region; in Purāṇic thought this supports context-sensitive dharma—rulers and householders should govern and live according to the capacities and conditions of their land and people.
No explicit Vāstu or ritual rule is stated, but the term pramāṇa (measure) can be read as a cosmographic ‘standard of measure’ or bodily stature—background concepts that later inform proportional thinking in iconography and temple measurements.