Matsya Purana — Measures of Time: Caturyuga Computation
इत्येतदृषिभिर्गीतं दिव्यया संख्यया द्विजाः दिव्येनैव प्रमाणेन युगसंख्या प्रकल्पिता //
ityetadṛṣibhirgītaṃ divyayā saṃkhyayā dvijāḥ divyenaiva pramāṇena yugasaṃkhyā prakalpitā //
Thus, O twice-born ones (dvijas), this has been sung by the sages in a divine system of numbers; by that very divine standard of measure, the computation of the yugas has been set forth.
It does not describe pralaya directly; it establishes that yuga chronology is based on a “divine” standard of measurement, which underlies Purāṇic cycles of creation and dissolution.
By grounding yuga counts in authoritative sacred measures, it supports the Purāṇic idea that dharma (royal and household duties) varies by age; knowing the yuga framework helps interpret which practices are emphasized in a given era.
No specific Vāstu rule is stated, but the verse highlights “divine measures” (pramāṇa), a concept echoed in ritual timing (muhūrta) and in Vāstu/śilpa traditions where correct measurement is considered sacred and authoritative.