Matsya Purana — Śrāddha Procedure: Types
पुनर् भोजनमध्वानं यानमायासमैथुनम् श्राद्धकृच्छ्राद्धभुक्चैव सर्वमेतद्विवर्जयेत् //
punar bhojanamadhvānaṃ yānamāyāsamaithunam śrāddhakṛcchrāddhabhukcaiva sarvametadvivarjayet //
One should avoid all of the following: eating again (a second meal), long travel, riding or vehicular movement, exhausting exertion, sexual intercourse, undertaking a Śrāddha-related austerity (kṛcchra), and eating the food offered in a Śrāddha.
This verse does not address pralaya; it focuses on personal discipline and purity rules connected with Śrāddha (ancestral rites).
It gives ācāra (conduct) restrictions—avoiding repeat eating, travel, exertion, and sexual activity—so a householder (and by extension a ruler observing dharma) maintains ritual purity and mental steadiness when connected with Śrāddha observances.
The significance is ritual: it lists actions to be avoided in connection with Śrāddha, emphasizing restraint and purity; it has no direct Vāstu or temple-architecture instruction.