The quipu is a traditional Andean counting device that uses colored strings and knots in lieu of paper and numbers.

When the Spanish Conquistadors encountered the mighty Inca empire, they found thousands of knotted-up ropes called quipus.

The Incas had a system of accounting that relied on the quipu. Cords of various colours were attached to a main cord with knots. The number and position of knots as well as the colour of each cord ...