quipu

‖n.; pl. Quipus [ Peruv. quipu a knot. ] A contrivance employed by the ancient Peruvians, Mexicans, etc., as a substitute for writing and figures, consisting of a main cord, from which hung at certain distances smaller cords of various colors, each having a special meaning, as silver, gold, corn, soldiers. etc. Single, double, and triple knots were tied in the smaller cords, representing definite numbers. It was chiefly used for arithmetical purposes, and to register important facts and events. [ Written also quipo. ] Tylor. [ 1913 Webster ]

The mysterious science of the quipus . . . supplied the Peruvians with the means of communicating their ideas to one another, and of transmitting them to future generations. Prescott. [ 1913 Webster ]