"The World's Greatest Inventor, World's Greatest Damn Fool"
(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.
Stross, Randall E. The Wizard of Menlo Park: How Thomas Alva Edison Invented the Modern World. New York: Crown Publishers, 2007.