Incan Counting System Decoded? By Rossella Lorenzi, Discovery News Learn how to add 9+7 on the yupana abacus. Jan. 29, 2004 ? The Inca invented a powerful counting system that could be used to make complex calculations without the tiniest mistake, according to an Italian engineer who claims to have cracked the mathematics of this still mysterious ancient population. Begun in the Andean highlands in about 1200, the Inca ruled the largest empire on Earth by the time their last emperor, Atahualpa, was garroted by Spanish conquistadors in 1533. Long been considered the only major Bronze Age civilization without a...