All  

knots

An Inca quipu, from the Larco Museum in Lima, Peru.

Researchers Say New Find of Khipu Strings May Help Unravel the Inca Record-keeping System

Archaeologists have discovered a collection of khipu (quipu) —a system of colored strings and knots people used to record various matters and send messages in the pre- and post-colonial eras in Peru—...
Incas counting gold - Ancient Mathematical Device

Quipu: The ancient mathematical device of the Inca

A team of archaeologists recently discovered twenty-five well preserved quipus, an ancient form of record-keeping used by the Inca, in the archaeological complex of Incahuasi in Peru, according to a...