1964.10.27 Knowing things that aren't so
Ronald Reagan delivered a speech on television that contained a quote, "Well, the trouble with our liberal friends is not that they are ignorant, it's just that they know so much that isn’t so!"
History of the Quote
This quote far predates Reagan. There are two forms attributed to Mark Twain, though it far predates him:
The quote has also been attributed to Josh Billings, Artemus Ward, Will Rogers and others. But it's been rewritten and paraphrased, and the oldest usage found was from Josh Billings in 1874, "I honestly believe it is better to know nothing than to know what ain’t so" (though he used archaic/dialectical spelling). But that was in a book section about aphorisms, implying he was quoting things that far predated him, not that he actually created them.  So Reagan gets credit for the quote as often used in popular culture, as it was an old aphorism, repurposed and brought into common popular and modern usage by him.