The sciences subsumed within the Tibetan category tsi (rtsis), "calculation," include calendrical reckoning and astrology (kartsi; dkar rtsis) and, secondly, elemental divination (naktsi; nag rtsis). The former is essentially based on the Kālacakra, a late tantra that was introduced from India in the twelfth century, and the latter on Chinese precedents. Although scholarly literature concerning the Tibetans' assimilation of these sciences is steadily growing, there has so far been almost no discussion of the way in which they have been adopted into the Bon religion. Using the example of the educational curriculum of a Bonpo monastery in India, this article explores the pedagogical context within which astrology and (to a lesser extent) elemental divination are taught to young monks. A number of didactic works are then examined with a view to discerning their distinctively Bonpo features.