sentences:  This device started him thinking about calculating machines and this point really marks the birth of the Monroe calculator.In the office of a life insurance company at St. Louis, he had seen an arithmometer, a calculating machine devised by Charles Xavier Thomas around 1820 and which, at the time, was the only mechanical desktop calculator in commercial production.To create a model based on his ideas he hired William Seward Burroughs I to perform the work in his machine shop, which he, with his father, had in St. Louis.