Matsya Purana — Rite and Layout for Consecrating Ponds
कूर्मादि स्थापयेन्मध्ये वारुणं मन्त्रमाश्रितः ब्रह्माणं च शिवं विष्णुं तत्रैव स्थापयेद्बुधः //
kūrmādi sthāpayenmadhye vāruṇaṃ mantramāśritaḥ brahmāṇaṃ ca śivaṃ viṣṇuṃ tatraiva sthāpayedbudhaḥ //
Invoking the Vāruṇa mantra, the wise officiant should install the supporting emblem beginning with the Tortoise in the centre; and in that very place he should also establish Brahmā, Śiva, and Viṣṇu.
It does not describe Pralaya directly; instead, it preserves cosmic order symbolically by placing foundational supports (like Kūrma) and the Trimūrti at the centre—an architectural mirror of stable creation.
It frames a duty of patronage and correct ritual practice: a king or householder supporting temple consecration should ensure mantras and placements are done properly by a learned officiant, reflecting dharma through orderly worship.
It gives a Vāstu-pratiṣṭhā rule: the centre is ritually charged by installing a Kūrma-like support and establishing Brahmā, Śiva, and Viṣṇu there, with the Vāruṇa mantra as the empowering recitation.