The little versified treatise on the elements of Buddhist logic, often referred to as the Hetucakraḍamaru, is usually attributed to Dignāga. It is only available in a Tibetan translation and quotations from a few of its verses are extant in Sanskrit sources. On the basis of a novel interpretation that is based on a critical edition of the text, we argue that there is a good reason why its title was Hetucakraḍamaru - a ḍamaru is a two-headed drum. The “heads” (...) of the drum are circular and they refer to the sapakṣa and vipakṣa conditions of the logical reason. These “wheels” can be turned clock-wise and counter clock-wise. The nine positions that are located on the wheels do remind one of a dharmacakra, which has a center and eight positions that are placed around it as if it were a compass. We illustrate our interpretation of the text by means of various diagrams. (shrink)