(p. 290) One of his employees recalled walking past him one day as the inventor stepped briskly between buildings at the lab. He cheerfully greeted his employer: “Morning, Mr. Edison.” Edison gave him a glance, raised his finger to show a major pronouncement would follow, and said, “The world’s greatest inventor, world’s greatest damn fool,” then hurried on.
Source:
Stross, Randall E. The Wizard of Menlo Park: How Thomas Alva Edison Invented the Modern World. New York: Crown Publishers, 2007.