Quipus pl. : of Quipu

Example:
The Inca religious center discovered on a mountaintop in 1911 was: A Cuzco B Quechua C Machu Picchu D Quipus?

Taxonomy
quipus, knots, Inca quipu, cords, Inca, Khipu, Quipucamayocs, knotted cords, strings, Conservation, digit, Frank Salomon, Ascher, Ordish, Rapaz, damage, New York, eight knots.

Defination from the web:
quipus were used basically as mnemonic devices to communicate and record information in the numerical format. ... The treasure hunt of Clive Cussler's Dirk Pitt novel Inca Gold centers on the decryption of a quipu's message. ...