Matsya Purana — Agastya’s Origin
आ सप्तरात्रोदयम् एतदस्य दातव्यमेतत्सकलं नरेण यावत्समाः सप्त दशाथवा स्युर् अथोर्ध्वमप्यत्र वदन्ति केचित् //
ā saptarātrodayam etadasya dātavyametatsakalaṃ nareṇa yāvatsamāḥ sapta daśāthavā syur athordhvamapyatra vadanti kecit //
Up to the completion of seven nights, a man should give all of this as prescribed—continuing for seven years, or for ten years; and some authorities even speak of continuing beyond that.
This verse does not discuss Pralaya; it focuses on dharmic procedure—how long a prescribed giving/observance should be maintained (seven nights as a unit, extended across years).
It frames a disciplined pattern of dāna and vrata: the performer should complete the prescribed gifts through a seven-night cycle and sustain the practice for a long term (seven or ten years, or more), reflecting steadiness and accountability expected of householders and rulers alike.
The significance is ritual (not architectural): it specifies the temporal discipline of an observance—completion of a seven-night cycle and its recommended long-term continuation, with acknowledgment of differing traditional opinions.