From the 100 Facts for 100 years of Machu Picchu- Fact #4

By Catharine Hamm Los Angeles Times Travel Editor

4. The Inca used khipu (spelled "quipu" in Spanish), a series of knots that functioned as a sort of counting system.

 The Khipu was first used by the Huari people who flourished in the southern and central region of Peru from 500 - 1000 AD.  Many of the Huari practices were later adapted by the Incas and incorporated into their society including the use of the Khipu, terracing the mountain side for agricultural purposes as seen at in the Sacred Valley and Machu Picchu as well as the use labor as a tribute to the state.