I wasn't sure what you were trying to saying there so I looked it up:
To further assure that he would not lapse into sleep, he would hold a steel ball bearing in each hand. On the floor, placed directly below his closed hand would be a metal saucer. If he should fall completely asleep, his hands would relax and each ball bearing would fall to the floor, striking the metal saucer, making a noise loud enough to wake Edison.
To further assure that he would not lapse into sleep, he would hold a steel ball bearing in each hand. On the floor, placed directly below his closed hand would be a metal saucer. If he should fall completely asleep, his hands would relax and each ball bearing would fall to the floor, striking the metal saucer, making a noise loud enough to wake Edison.
1. https://fireballimagery.com/2011/09/01/the-naps-of-thomas-ed...