Common history myths and how they spread: horned helmets, Napoleon and more

Some of the best-known facts about the past are wrong, and the interesting question is not just what is false but how the mistake took hold. These well-documented examples show the usual routes: art and entertainment, propaganda, misunderstood units, convenient anecdotes and later writers with a point to make.

There is no evidence that Viking warriors wore horned helmets in battle. The only near-complete helmet surviving from the Viking Age, found at Gjermundbu in Norway in 1943, is a rounded iron cap with a spectacle-like guard and no horns. Horned helmets that do exist from Scandinavia, such as those found at Viksø in Denmark, date from the Bronze Age, many centuries before the Vikings. The image owes much to the 19th century. Carl Emil Doepler's costume designs for the first complete staging of Wagner's Ring cycle at Bayreuth in 1876 gave characters horned headgear, and it spread through illustration, theatre and later film and advertising. How it spread: romantic art and popular culture, reinforced by mixing up objects from very different periods.

Napoleon's height was recorded in French units as five feet two inches. The French inch, or pouce, was longer than the English inch, so the figure converts to roughly 1.68 metres, about five feet six in English measure. That was around average or slightly above for a French man of his time. The myth was helped by British caricaturists, notably James Gillray, who drew him as a tiny figure throwing tantrums during the wars between the two countries. His nickname, the Little Corporal, was an affectionate one from his soldiers, not a comment on his height. How it spread: a units confusion, wartime propaganda and a misread nickname.

Educated people in medieval Europe knew the earth was a sphere, as the ancient Greeks had shown. The scholars who doubted Columbus were worried that he had underestimated its size, and they were right; he was saved by landing in the Americas. The historian Jeffrey Burton Russell, in his 1991 book Inventing the Flat Earth, traced the myth largely to the 19th century. Washington Irving's romanticised 1828 biography of Columbus helped popularise the picture of churchmen insisting the world was flat, and later writers presenting history as a war between science and religion repeated it. How it spread: a dramatic story in a popular book, then use as ammunition in a later argument.

There is no evidence she said it. A similar line appears in Jean-Jacques Rousseau's Confessions, where an unnamed "great princess" suggests that peasants with no bread should eat brioche. Rousseau wrote that part in the 1760s, when Marie Antoinette was still a child in Austria. The attribution to her appears in print only decades after her death. How it spread: a story that fitted the image of an out-of-touch queen became attached to the most famous candidate.

Myths are part of history too: studying how and why they spread tells you a great deal about the period that believed them. Which history myth did you believe longest? Share it, with your best source, in the comments.