Primary Source
(Retrieved from http://en.wikipedia.org/wiki/Quipu on November 3, 2014.)
The image to the above is a picture of the Inca's way to keep track. It is called a Quipu. It is how Inca accountants kept track of the population, cattle, and food.
(Retrieved from google.com/maps on November 12, 2014.)
Image: Map showing where the Inca lived. You can go there on vacation.