Matsya Purana — Bhīma-Dvādaśī
तथैव विष्णोः शिरसि क्षीरधारां प्रपातयेत् अरत्निमात्रं कुण्डं च कुर्यात्तत्र त्रिमेखलम् //
tathaiva viṣṇoḥ śirasi kṣīradhārāṃ prapātayet aratnimātraṃ kuṇḍaṃ ca kuryāttatra trimekhalam //
In the same manner, one should pour a continuous stream of milk upon the head of Viṣṇu. And one should also construct there a kuṇḍa (fire-pit) of the measure of one aratni (forearm), furnished with three enclosing girdles (tri-mekhalā).
This verse is not about pralaya; it prescribes a consecration-style ritual act—pouring milk over Viṣṇu’s head—and gives construction details for a small ritual kuṇḍa.
It reflects the householder/royal duty of maintaining proper temple worship and public rites: performing abhiṣeka correctly and building ritual facilities (like a measured kuṇḍa) according to śāstric specifications.
It specifies a standard ritual setup: a one-aratni kuṇḍa and a tri-mekhalā (three-banded/three-stepped enclosure), alongside milk-abhiṣeka to Viṣṇu—details relevant to Puranic temple ritual and Vāstu-aligned construction.