Only one - Abraham Lincoln.
In 1849, then-attorney Abraham Lincoln was granted Patent No. 6,469 for a device that could be filled with air to allow a ship to pass through shoals or shallow water.
Lincoln's law partner, William Herndon, wryly observed, "The invention was never applied to any vessel, so far as I ever learned, and the threatened revolution in steamboat architecture and navigation never came to pass."
In 1849, then-attorney Abraham Lincoln was granted Patent No. 6,469 for a device that could be filled with air to allow a ship to pass through shoals or shallow water.
Lincoln's law partner, William Herndon, wryly observed, "The invention was never applied to any vessel, so far as I ever learned, and the threatened revolution in steamboat architecture and navigation never came to pass."