A “khipu” is the basis for a treasure map in the Clive Cussler novel “Inca Gold”. The “khipuy” (or “quipu”, as the novel refers to it) is used to delineate direction and distance to the treasure that is the basis of the story.
:’) It’s been said that the knotting system was probably a mnemonic of some kind, or perhaps abacus-like for storing numbers. One supposed eyewitness of one being used had the user following the strings one by one, not even looking at them, and reciting stuff.