Fact Check: Mark Twain Once Said

Fact Check: Mark Twain Once Said 'No Amount of Evidence Will Ever
Persuade an Idiot'?

Context:

Multiple points of data, all spelled out below, show that mentions of
this quote with Twain's name appeared to be born on the internet
during or prior to the year 2012.
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Twain's Real Thoughts About 'Evidence' and 'Idiots'

While there's no record of Twain ever saying the exact words in the
quote, the word "evidence" did appear in his writings.

For example, in Twain's 1896 novel, "Personal Recollections of Joan of
Arc," he wrote, "It was not my opinion; I think there is no sense in
forming an opinion when there is no evidence to form it on. If you
build a person without any bones in him he may look fair enough to the
eye, but he will be limber and cannot stand up; and I consider that
evidence is the bones of an opinion."

Also, in a letter dated March 23, 1898, Twain, referred to by his real
name, Clemens, wrote to wealthy businessman Henry Huttleston Rogers,
saying that, "Circumstantial evidence is among the most valuable of
all testimonies." The letter appears on page 336 of the book, "Mark
Twain's Correspondence with Henry Huttleston Rogers, 1893-1909."

 https://www.yahoo.com/news/fact-check-mark-twain-once-140000593.html