Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
एकादश्यां च नक्ताशी यश्चक्रं विनिवेदयेत् समान्ते वैष्णवं हैमं स विष्णोः पदमाप्नुयात् एतत् कृष्णव्रतं नाम कल्पान्ते राज्यभाग्भवेत् //
ekādaśyāṃ ca naktāśī yaścakraṃ vinivedayet samānte vaiṣṇavaṃ haimaṃ sa viṣṇoḥ padamāpnuyāt etat kṛṣṇavrataṃ nāma kalpānte rājyabhāgbhavet //
Whoever, on Ekādaśī, eats only at night and offers to Viṣṇu a golden discus (cakra), in due course attains the supreme abode of Viṣṇu. This observance is called the Kṛṣṇa-vrata; at the end of the kalpa one becomes a sharer in sovereignty (royal fortune).
It does not describe Pralaya directly; it uses the phrase “kalpānte” (end of the aeon) to express the long-range, cosmic-scale merit (phala) of a Vaiṣṇava vow leading to Viṣṇu’s abode and eventual sovereignty.
It prescribes a householder-friendly discipline—Ekādaśī night-only eating (naktāśī) with a devotional offering—promising spiritual attainment and also worldly fruition (rājyabhāg), aligning personal piety with dharmic prosperity.
The ritual detail is the offering of a golden Vaiṣṇava cakra (Sudarśana emblem), indicating iconographic/ritual gifting practices (dāna and pūjā-upacāra) associated with Viṣṇu worship rather than Vāstu or temple-construction rules.