William James Sidis, a prodigious figure in the annals of intellectual history, is often referred to as one of the smartest people who ever lived. Some reports have estimated his IQ, a measure of intelligence, to range in the mind-boggling numbers between...

In 1908 — about a century before the iPhone — inventor Nikola Tesla mused about creating a device "no bigger than a watch" that would allow someone to hear "music or song [or] the speech of a political leader" and transfer "any picture, character, drawing...