Nikola Tesla's AC vision

“One afternoon I was walking with a friend in the City Park and reciting poetry. At that time I knew entire books by heart, word for word. One of these was Goethe’s “Faust;” and the setting sun reminded me of the passage:

“The glow retreats, done is the day of toil; It yonder hastes, new fields of life exploring; Ah, that no wing can lift me from the soil, Upon its track to follow, follow soaring!“
“Even while I was speaking these glorious words, the vision of my induction motor, complete, perfect, operable, came into my mind like a flash. I drew with a stick on the sand the vision I had seen. They were the same diagrams I was to show six years later before the American Institute of Electrical Engineers. My friend understood the drawings perfectly; and to me the images were so real that suddenly I cried, “Look! Watch me reverse my motor!” And I did it, demonstrating with my stick.

This discovery is known as the “rotating magnetic field.” It is the principle on which my induction motor operates.”

–Nikola Tesla
“Making Your Imagination Work For You.” American Magazine, April, 1921.