Dayton, Ohio saloonkeeper James J. Ritty knew his bartenders were stealing from his moneybox, but since his was a cash business, he had no way of knowing how much he was losing. Their pilfering bothered him so much that it undermined his health. So he went on a sea cruise to Europe to recuperate. While aboard ship, he grew fascinated by a device that recorded the revolutions of the boat's propeller. It gave the captain an accurate record of the ship's speed throughout the day. That inspired Ritty to develop a machine to help him record saloon transactions throughout the day. On November 4, 1879, he patented Ritty's Incorruptible Cashier, the world's first mechanical cash register. He eventually sold his business and patent rights for $31,000 to a firm that became the National Cash Register Company, known years later as NCR.