Julius Caesar did not coin the phrase "The die is cast", which he remarked before crossing the Rubicon. According to Plutarch, the phrase was common even in Caesar's day, having been used by the Greek dramatist Menander. Furthermore, there is some doubt whether Caesar even said this phrase, as he does not mention using this phrase in his writings. (source)

Canute (also spelled Knut), King of England (1016–1035) and of Denmark and Norway for most of that time, is well-known for having ordered the tide to retreat. However, he did not do so because he believed that he could actually stop it. He did it to demonstrate to sycophants that he was not omnipotent.

Nowhere in the nursery rhyme "Humpty Dumpty" does it state that Humpty Dumpty was an egg. (source)

It is not true that the early Chinese used gunpowder only for fireworks. They had forms of guns (invented in 1288), bombs, grenades, rockets, landmines, flamethrowers, small cannons, and other weapons.

Few witches were burned during the Middle Ages; most witch-burnings happened in later centuries.

In the fifteenth century, Prince Henry the Navigator dispatched his sea captains on voyages to explore the African coast. One of Henry's hopes was that his men would discover the rich Christian kingdom of "Prester John", which was supposedly cut off from the rest of Christendom due to the Islamic conquest. Eventually, after Henry's death, the Portuguese rounded the Cape of Good Hope and sailed the east coast of Africa, only to find that Prester John's kingdom did not really exist. While they found a Christian kingdom in Ethiopia, it was dismissed as being that of Prester John due to its poverty. (source)

The Emancipation Proclamation freed very few slaves immediately. Issued by Abraham Lincoln on January 1, 1863, the proclamation applied only to slaves in areas controlled by the rebel Confederate government, where Lincoln had no authority to enforce it. (source)

In 1903, Albert Michelson, one of the 19^th century's top physicists, commented "The more important fundamental laws and facts of physical science have all been discovered, and these are so firmly established that the possibility of their ever being supplemented in consequence of new discoveries is exceedingly remote". Two years later, Einstein published his revolutionary Theory of Special Relativity.

As late as 1820, the universe was thought by European scientists to be 6,000 years old. It is now thought to be about 13,700,000,000 years old. (source)

The Eastern side of the Panama Canal connects to the Atlantic Ocean and the Western side of the canal to the Pacific, not the other way around. (source)

Ostriches never bury their heads in sand. (source)

The White House did not obtain its name because it was painted white after being burned by the British in the War of 1812. The building was already known as the "White House" before the sack of Washington in 1814. (source)

In 1985, NASA estimated the probability of a space shuttle accident to be 1 in 100,000. However, on the 25^th shuttle launch on January 28, 1986, Challenger exploded after take-off, killing all seven astronauts aboard; again, on February 1, 2003, the 113^rd mission, Columbia exploded on re-entry, again with the loss of all seven astronauts. Other groups had earlier estimated the probability of failure as being closer to 1 in 100, a probability that in retrospect seems more reasonable.

Heart attacks generally do not kill people. It is the complications from heart attacks, such as scarring of the heart tissues, that kill. (source)

The Sahara, the world's largest desert, is not the largest sand desert. Only 15% of the Sahara is sand dunes, while over 70% consists of stone desert. The largest sand desert is the Great Arabian Desert, or Rub-al-Khali, in the Arabian Peninsula. (source)

When Sir Thomas More's Utopia was first published, the learned Budæus and others took it for a genuine history of an island that supposedly had been recently discovered in America, and suggested that missionaries be sent there to convert such a wise nation to Christianity. (source)

It is untrue that carrots are good for your eyes. This belief started in World War II, when the British began using airborne radar, allowing them to find German bombers at night. In order to mislead the Germans, a rumour was spread indicating that John Cunningham, the Royal Air Force's most successful night fighter pilot, had developed phenomenal night sight by eating carrots in large quantities.

Abner Doubleday did not invent the game of baseball. The story of his invention of the game was created many years later based on hearsay and credited to Doubleday due to his fame as a general in the Civil War. Alexander Cartwright, a New York City bank clerk who devised several changes to the American form of rounders in 1844, is probably the best candidate for the inventor of baseball. (source)

It isn't true that most people only use 10% of their brain. This myth dates back to around 1900, when psychologist William James wrote that he doubted that average persons reach more than 10% of their intellectual potential. While James never equated intellectual potential to what portion of the brain was engaged, Lowell Thomas implied in 1936 that that was what James said. (source)

Dinosaurs did not eat grass. Grass evolved from bamboo-like plants only 24 million years ago, 40 million years after the dinosaurs died out.

Napoleon was not particularly short. He was 5 feet 6½ inches tall, which was a typical height at the time. This height is equal to 5 feet 2 inches in old French feet (pieds du roi), which led to confusion as to his true height. (source)

It is not true that Einstein was a terrible student as a youth. While he was slow to learn to speak before entering school and did poorly at French while in school, his academic records indicate that he was a child prodigy who understood college physics before his eleventh birthday, a strong violin player, and skilled in Latin and Greek. (source)

It isn't true that many of the strange, outdated laws that are still on the books in various jurisdictions are never enforced. In 1999, after falling out of his canoe on the Rifle River in Michigan, a 25-year-old man was convicted for violating an 1897 law prohibiting cursing in front of women and children, and sentenced to four days' work in a child-care program plus a $75 fine. However, the law was struck down by the Michigan Court of Appeals in 2002 and the conviction thrown out. (source)

The phrase "Beam me up, Scotty" was never uttered during an episode of Star Trek. (source)

A peanut is not a nut. It is a member of the pea family. (source)

The original boomerangs, used by Australian aboriginals, did not return. They were used for hunting, where returning would be disadvantageous. (source)

The primary aim of the Inquisition, which operated between the twelfth and fifteenth centuries, was the conversion of heretics, not their destruction. A person would only be considered a heretic if they persisted in their views after three detailed cautions. Even then, that did not always lead to being burned at the stake or otherwise executed; some Inquisitors never passed a single death sentence. (source)

The Wright Brothers did not fly the first manned airplane. On August 14^th, 1901, a man named Gustav Albin Whitehead (born Weisskopf) flew a plane around half a mile (800 metres). However, without documentation such as photographs to support his claim, there was significant scepticism about his claim and it was not taken seriously. (source)

In the northern hemisphere, the sun is further away from the Earth in the summer than it is in the winter.

Voltaire never said the quotation for which he is well known—"I disapprove of what you say, but I will defend to the death your right to say it." It was created by Evelyn Beatrice Hall (who wrote under the pseudonym S. G. Tallentyre) in her 1906 book The Friends of Voltaire to illustrate an attitude that Voltaire may have held. (source)