William James Sidis was a wonder child; at eighteen months he could read The New York Times, at two he taught himself Latin, at three he learned Greek. By the time he was eight he had taught himself eight languages (Latin, Greek, French, Russian, German, Hebrew, Turkish, and Armenian). He also invented another, which he called Vendergood.
Youngest student at Harvard
William James Sidis gained entrance to Harvard at eleven, and gave a lecture on four-dimensional bodies to the Harvard Mathematical Club his first year. He earned his Bachelor of Arts degree, cum laude, on June 18, 1914, at age 16.
Shortly after graduation, he told reporters that he wanted to live the perfect life, which to him meant living in seclusion. He granted an interview to a reporter from the Boston Herald, which published his vows to remain celibate and never to marry, and a statement that women did not appeal to him (however, he later developed a strong affection for a young woman named Martha Foley). He later enrolled at Harvard’s Graduate School of Arts and Sciences.
Source:
http://www.prometheussociety.org/articles/Outsiders.html
http://en.wikipedia.org/wiki/William_James_Sidis

(5 votes, average: 4.2 out of 5)
The 250-300 IQ claimed by Wikipedia and “The Outiders” (at Prometheus) are based on wrong information derived from Amy Wallace’s book “The Prodigy: A Biography of William James Sidis, America’s Greatest Child Prodigy”. “The Prodigy” claimed that Sperling said: “In recent years I have tested more than five thousand people. Of all the mentally superior individuals that I have seen, nobody begins to approach the intellect and perspicacity of William Sidis. According to my computations, he easily had an IQ between 250 and 300.” Sperling’s own version, found in “A Story of Genius”, is: “Helena Sidis told me that a few years before his death, her brother Bill took an intelligence test with a psychologist. His score was the very highest that had ever been obtained. In terms of I.Q., the psychologist related that the figure would be between 250 and 300.” According to Sperling’s version, he based his comments on hearsay from Helena. Helena may have stretched the truth like she reportedly did with other claims about William Sidis’ language skills, which were recorded in “The Prodigy” as fact. No known adult IQ test exists today that can accurately measure 250-300, and none existed in the 1940s. The 250-300 IQ claim is a myth. The other claims of newspaper reports and Sidis’ language skills are mostly misleading half-truths and misinterpretations. Source: Myths, Facts, and Lies About Prodigies - A Historiography of Willia James Sidis.