Some old South American Indian cultures calculated on quipus, which were necklace-like objects where they would tie on the dangling strings different kinds of knots to indicate a number. The type and placement of the knots indicated the number. Subtraction involved untying knots. It was commonly used for accounting, trade and other business. The conquering Spanish didn’t fully understand quipus and thought that secret messages might be sent on them, and also considered them idolatry, so detroyed any that the found.