Years ago I read about Tesla that he would visualize a machine in his head, start a simulation of it running, then come back later and inspect the screws for wear - all of this in his imagination. Does anyone know whether that story is true? or where it came from?

Tesla told his story to the author of "Prodigal Genius" (1944), who wrote: "What Tesla had discovered was a means of creating a rotating magnetic field, a magnetic whirlwind in space which possessed fantastically new and intriguing properties...It was not necessary for him to construct models of copper and iron: in his mental workshop he constructed them in wide variety...The mental constructs were built with meticulous care as concerned size, strength, design and material; and they were tested mentally, he maintained, by having them run for weeks-after which time he would examine them thoroughly for signs of wear."

You nailed it. Yay! Thanks.

The full text of "Prodigal Genius", a somewhat hagiographic but still fascinating biography of Tesla, is online at http://www.rastko.rs/istorija/tesla/oniell-tesla.html.

Here's a cool documentary on Tesla:

Tesla: Master of Lightning http://www.pbs.org/tesla

http://www.youtube.com/watch?v=m1LqxG49DLk

And a vampire! He is probably reading this! :-D