Encyclopedia of the Incas

records show that the Incas employed a wide range of arithmetical operations,
including addition, subtraction, multiplication, and division, as well as the
calculation of fractions and ratios. Inca accountants and mathematicians knew
the concept of zero and used it in their calculations and recording of statistical
data.
While numerical data were recorded on the quipu, this device was not used for
performing calculations. Rather, colonial era chroniclers’ accounts and
administrative documents attest that calculations were performed by means of a
variety of counting devices, such as stones, maize kernels, or other small objects.
Calculations with these devices were carried out on stone, ceramic, or wooden
objects called yupana, square- or rectangular-shaped slabs containing numerous
depressions or compartments within which the counting devices were moved in
the process of calculating. Once the calculations were completed, the resulting
values would be knotted into quipus for display and transport.