Adding machine was patented in 1888 by W. S. Burroughs. He received patent number 388,116. Children could view his patent at: Adding Machine.
Comptometer, the first accurate adding machine, was patented by Dorr Eugene Felt in 1887. Made from a macaroni box and rubber bands, the prototype earned patent number 371,496. Felt and his partner became financially successful, and he held 46 other patents. The original macaroni box prototype is now part of the Smithsonian collection. Older children could learn more at: Comptometer.