Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
शीलवृत्तगुणोपेतान् वयोरूपसमन्वितान् द्वौ दैवे त्रींस्तथा पित्र्य एकैकमुभयत्र वा //
śīlavṛttaguṇopetān vayorūpasamanvitān dvau daive trīṃstathā pitrya ekaikamubhayatra vā //
One should choose (Brāhmaṇas) endowed with good conduct, proper livelihood, and virtues—also possessing suitable age and appearance: two for the offering to the gods, three for the offering to the ancestors; or else one each for both rites, or a single one for both.
This verse does not discuss pralaya; it focuses on ritual procedure—specifically, the proper selection and number of qualified invitees for daiva and pitṛ offerings.
It outlines a householder’s (and by extension a king’s) dharmic duty to perform śrāddha and related offerings correctly—honoring gods and ancestors by inviting morally qualified Brahmanas in the prescribed number.
The significance is ritual, not architectural: it prescribes the qualifications (character, conduct, virtues, suitable age/appearance) and the count—two for daiva-kārya, three for pitṛ-kārya, or one each when combining.