Originally, the term "computer" referred to a person who performed numerical calculations under the direction of a mathematician, possibly with the aid of a variety of mechanical calculating devices such as the abacus onward. Examples of early calculating devices, the first ancestors of the computer, included the abacus and the Antikythera mechanism, an ancient Greek device for calculating the movements of planets, dating from about 87 BCE. The end of the Middle Ages saw a reinvigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of European engineers to construct a mechanical calculator.