The hypothesis according to which “many of the Vedic identifications might be understood as metaphors“ was already advanced thirty years ago. The fresh approach of this paper consists in verifying a supposed cultural and technical connection of the earliest conceptualizing of the rūpaka as an extendend homology with the ritual and speculative procedures of substitution, rearranged by the Vedāṅga and Darśana-traditions. The structure of some late Vedic passages based on nature imagery is compared with the most ancient śāstra-definitions of this alaṃkāra, by paying special attention to the relationship between the whole and its parts. A Vārttika of Kātyāyana is attributed the value of a source of inspiration to the alaṃkāraśāstra-writers for the exceptional role accredited to the upamāna inside the rūpaka. The remote background of this research has to be recognized in the inquiry into the origin of Kāvya-literature.