Another side to this may be... I have read elsewhere that his mother taught him to visualize shapes at a very young age.

Note that another person who could visualize all the parts to his creations before he built them was Moses Browning. If you think about it, the ability may not have been all that rare. It just didn't have a lot of application before complicated machines.

As I recall, when Mr. Tesla was asked what it was like to be the smartest man in the world he replied "ask Michael Polanyi". I well know about the engineering of Mr. Tesla and his engineering "descendants" to today. For humanity to survive into the future we will also have to know what Mr. Polanyi and his "associates" learned.