Instead of writing, the Inkas’ principal bureaucratic tool was the khipu. A khipu consists of a number of strings or cords, either cotton or wool, systematically punctuated with knots, hanging from a master cord or length of wood; pendant cords might also have subsidiary cords. The basis of khipuaccounting practice was the decimal system, achieved by tying knots with between one and nine loops to represent single numerals, then adding elaborations to designate 10s, 100s or 1,000s. – Aeon