How did the Inka Calculate? The Yupana, a Mysterious Peruvian Abacus

Unlike the Chinese, Japanese and Russian bead frames, the Peruvian abacus is unknown even to many experts. Despite decades of research, it is still unclear how the Inka used this enigmatic digital calculating device. This is because there are hardly any contemporary descriptions. In addition, the abacus mentioned in the literature differs greatly from the finds made in Peru and Ecuador. In contrast to the knotted cords (quipus), which were used to store the results, only a few yupanas have survived. According to another interpretation, these mysterious objects were even models for urban planning.