How did Charles Lindbergh sleep when he flew from New York to Paris, nonstop, aboard his plane for more than 33 hours? He did not sleep due to the very high-tech system he developed to keep himself awake. He had not slept the night before and knew that staying awake on the 33-hour flight was going to be one of his major challenges. So, he got a heavy nut—the metal kind that goes on a bolt—and tied it to one finger with a string about a foot long. While at cruise altitude, he held the nut loosely in his fingers, palm down. When he dozed off, he’d drop the nut, which made the string tug on his finger and keep him awake. If it sounds crazy to have bet his life on a string yanking his finger, consider that he was flying a fabric-covered plane with no front window to see where he was going, with a single engine—and remember, that engine was built with 1920s technology—and navigating mostly by a bobbing wet compass. His wake-up device was one of the most reliable things on board.