It is without doubt that mathematics today owes a huge debt to the outstanding contributions made by Indian mathematicians over many hundreds of years. What is quite surprising is that there has been a reluctance to recognize this and one has to conclude that many famous historians of mathematics found what they expected to find, or perhaps even what they hoped to find, rather than to realize what was so clear in front of them. An abacus is a portable calculating device using a frame with rods that are strung with beads. Indigenous native Aztec and Maya people who lived in Mesoamerica, performed mathematical calculations using an abacus made from maize kernels, instead of beads, threaded on strings. It provided a faster and more accurate way of adding and subtracting than relying on memory alone. This abacus, which was called a nepohualtzitzin, had three beads on the top deck and four beads on the bottom. Archaeologists have dated the presence of such counters at about A.D. 900 to 1000. The Aztec abacus, which was devised without any knowledge of the Chinese abacus (invented about 500 B.C.), required the same level of critical thinking and knowledge of mathematics to develop. The Inca, whose empire was established in what is now Peru in about A.D. 1000, also were known to have a type of abacus. This consisted of a tray with compartments that were arranged in rows in which counters were moved in order to make calculations.