It's been accepted for quite a while that their knotted strings (khipu) were more than just decorative. Now a scholar is suggesting they contain complete books, like simplistic braille.

"Gary Urton, professor of anthropology at Harvard University, has re-analysed the complicated knotted strings of the Inca - decorative objects called khipu - and found they contain a seven-bit binary code capable of conveying more than 1,500 separate units of information.

In the search for definitive proof of his discovery, which will be detailed in a book, Professor Urton believes he is close to finding the "Rosetta stone" of South America, a khipu story that was translated into Spanish more than 400 years ago."