Matsya Purana — Cosmic Architecture of Sun–Moon and the ‘Houses of the Gods’
खद्योतरूपी विचरन्न् आविर्भावं व्यचिन्तयत् ज्ञात्वाग्निं कल्पकालादाव् अपः पृथ्वीं च संश्रिता //
khadyotarūpī vicarann āvirbhāvaṃ vyacintayat jñātvāgniṃ kalpakālādāv apaḥ pṛthvīṃ ca saṃśritā //
Moving about in the form of a firefly, he contemplated the manner of manifestation. Knowing the principle of Fire at the beginning of the kalpa, he resorted to the Waters and to the Earth.
It hints at the post-Pralaya re-manifestation process: a conscious principle contemplates emergence and, at the start of a Kalpa, relates the fire-principle to the foundational supports of waters and earth—signaling elemental reconstitution after dissolution.
Indirectly, it grounds dharma in cosmic order: rulers and householders are urged (elsewhere in the Matsya Purana) to align conduct, ritual, and governance with the rhythms of Kalpa and the stability of the elements—acting with foresight, restraint, and responsibility amid change.
While not a Vastu rule itself, the verse foregrounds the elemental triad (fire, water, earth) that later underpins ritual layout and Vastu logic—e.g., proper placement and balancing of agni (fire rites), ap (water features), and bhūmi (site/earth) in sacred and domestic spaces.