David Pingree's 1989 paper on planetary images, p. 5, describes the prescribed geometrical shapes of the plinths on which planetary images are to be mounted according to the Vaikhānasasmārtasūtra and the Agniveśyagṛhyasūtra. The shapes of the latter text are like those you list, Jacob.

Best,

Dominik

Dominik Wujastyk, Professor Emeritus, Classical Indian History

University of Alberta

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Current research: The Suśruta Project