Matsya Purana — Śrāddha Procedure: Types
पितृयज्ञं विनिर्वर्त्य तर्पणाख्यं तु यो ऽग्निमान् पिण्डान्वाहार्यकं कुर्याच् छ्राद्धमिन्दुक्षये सदा //
pitṛyajñaṃ vinirvartya tarpaṇākhyaṃ tu yo 'gnimān piṇḍānvāhāryakaṃ kuryāc chrāddhamindukṣaye sadā //
Having duly completed the Pitṛ-yajña—namely the rite called tarpaṇa—one who maintains the sacred fire should always perform the Śrāddha with piṇḍa-offerings and the anvāhārya-oblation at the waning of the moon (the new-moon period).
This verse is not about pralaya; it prescribes routine ancestral rites (pitṛyajña, tarpaṇa, śrāddha) and their proper timing, emphasizing continuity of dharma in ordinary time.
It primarily addresses the gṛhastha who keeps the sacred fires (agnimān): after performing tarpaṇa as pitṛyajña, he should regularly perform śrāddha with piṇḍa offerings, especially at the moon’s waning/new-moon period—an essential household duty supporting lineage and social-religious order.
The significance is ritual (not architectural): it specifies the śrāddha framework—tarpaṇa as pitṛyajña, piṇḍa offerings, and the anvāhārya-related oblation—performed at indukṣaya (new-moon/waning-moon time) as a regular observance.