The Organum Mathematicum

A 17th Century Computer

Athanasius Kircher (1602-1680) was a Jesuit scholar and polymath who was celebrated in his lifetime as one of the greatest geniuses of his age. He published on optics, magnetism, linguistics, hydraulics, and Egyptology, among many other subjects.
Here are photos of the organum mathematicum, one of his inventions. This one is owned by the Galileo Museum in Florence. It’s a combination of an encyclopedia and a calculator. The museum describes how it works:

The inside of the chest is divided into nine compartments, one for each of the following subjects: Arithmetic, Geometry, Art of fortifications, Chronology, Horography, Astronomy, Astrology, Steganography, and Music. Each compartment contains twenty-four small rods ending in a colored triangular tip. On each of the nine series of twenty-four small rods are inscribed definitions and information on the corresponding subject. At least one rod in each of the nine compartments has a black tip and constitutes the application table, which gives the rule for proper use. To multiply 74 x 8, for example, one removes the black-tipped rod from the Arithmetic compartment and places it next to the rods carrying the numbers 7 and 4 at the top. The eighth line on the black-tipped rod gives the desired product.