Matsya Purana — The Rite of Gifting the ‘Silver Mountain’
अशक्तो विंशतेरूर्ध्वं कारयेच्छक्तितस्तदा विष्कम्भपर्वतांस्तद्वत् तुरीयांशेन कल्पयेत् //
aśakto viṃśaterūrdhvaṃ kārayecchaktitastadā viṣkambhaparvatāṃstadvat turīyāṃśena kalpayet //
If one is unable to carry out (the prescribed work) beyond twenty (units), then it should be done according to one’s capacity. Likewise, the transverse measures (viṣkambha) and the raised portions (parvata) should be set in proportion by taking a quarter-share (turīyāṁśa).
This verse does not address Pralaya; it gives practical Vastu guidance on scaling construction measurements when one cannot follow the full prescribed dimension.
It frames dharmic practicality: a patron (king/householder) should undertake building works within means, maintaining proportional harmony rather than abandoning the project or violating core design ratios.
It authorizes proportional reduction—especially using a quarter-share rule (turīyāṁśa)—for key dimensions like breadth/diameter (viṣkambha) and raised elements (parvata), preserving canonical Vastu symmetry under constraints.