Portion of the Bush Product Integraph, ca 1925, Smithsonian Institution negative number NMAH-AHB2016q152378

By the early 20th century, engineers, physicists, and mathematicians were familiar with instruments that could integrate functions mechanically. Integraphs, which plotted the integral of a function, had sold for decades. The electrical engineer Vannevar Bush (1890–1974) and two of his MIT colleagues devised this instrument, designed to find the integral of the product of two functions. Both the functions and the integral of the product were drawn on sheets of paper (these sheets, and the table that held them, were not collected). From this start in the mid-1920s, Bush would go on to build room-sized differential analyzers—analog computing devices with even greater capabilities. He then became vice-president of MIT and would head the Office of Scientific Research and Development during World War II.

For a description of simpler instruments used to find the area bounded by plane curves, see https://americanhistory.si.edu/collections/object-groups/planimeters. For an account of integrators and differential analyzers, see https://americanhistory.si.edu/collections/object-groups/mechanical-integrators.