quipu

Device used by the Incas of ancient Peru to record numerical information, consisting of a set of knotted cords of one or several colours hanging from a top-band or crossbar. It was used to take stock of granary and warehouse stores, and also to record historical events and to communicate edicts and messages.

The number, size, position, distance apart, and colour of the knots on the quipu all had particular significance. Some other ancient peoples (in China and Tibet) and some contemporary peoples have also employed similar mnemonic devices of communication.

Modern research on the quipu system has shown that the Incas, like the Maya, had an advanced arithmetic that used the concepts of zero and place notation.