Matsya Purana — Procedure for Going to Prayaga and the Greatness of the Ganga
अङ्गिरःप्रमुखाश्चैव तथा ब्रह्मर्षयः परे तथा नागाः सुपर्णाश्च सिद्धाश्च खेचराश्च ये //
aṅgiraḥpramukhāścaiva tathā brahmarṣayaḥ pare tathā nāgāḥ suparṇāśca siddhāśca khecarāśca ye //
Led by Aṅgiras, and likewise other great Brahmarṣis; and also the Nāgas, the Suparṇas (Garuda-like beings), the Siddhas, and the Khecaras who move through the sky—all of them (were present/are enumerated).
It does not describe Pralaya directly; it catalogs the classes of exalted beings (rishis and celestial orders) who populate and witness the cosmic order that persists across cycles.
Indirectly, it frames an ideal of hierarchy and sacred order: kings and householders are urged elsewhere in the Matsya Purana to uphold dharma in harmony with the broader cosmic community overseen by rishis and divine beings.
No explicit Vāstu or ritual procedure appears in this line; its practical value is contextual—identifying the authoritative celestial/rishi milieu that later validates rites, consecrations, and sacred regulations.