Untying the knots of Incan codes

Quipus are the mysterious bundles of colored and knotted threads that served as the Inca empire's means of recording information. The code of the quipus has long since been forgotten, and the only major advance in understanding them was the insight, made in 1923, that the knots were used to represent numbers.

The quantity and positioning of the knots, at least in certain quipus, is agreed to represent a decimal system

Read the entire article at the Herald Tribune...
http://www.iht.com/articles/2005/08/18/features/INCA.php