The Often Misquoted

Photo: perpetualplum

I’m back to inviting readers to submit quotations whose origins they want me to try to trace, using my book, The Yale Book of Quotations, and my more recent researches.
Aaron asked:

I’ve heard that Ben Franklin was misquoted when he said ‘Jack of all Trades, Master of None,’ and that he actually said ‘Jack of all Trades, Master of Some.’  Is there any truth to this?

I believe neither of these sayings appears in Benjamin Franklin‘s writings.
Jaime asked:

Hello, I was recently reading up on an old interview with one of the greatest minds of last century, John A. Wheeler and in it he quotes:
‘The difference between the right word and the nearly right word is the difference between lightning and a lightning-bug.’
As having been originally presented to the world by Mark Twain, and, of course, I immediately started thinking about whether a world renown physicist, that got so much right in such an uncertain world (and coined words such as Black Holes himself), managed to get right a quote by one of the most often misquoted author ever.

Wheeler was correct that a very similar quotation appears in an 1888 letter of Mark Twain’s.  Note that it is not correct that Wheeler coined the term “black hole,” which appeared in print several years before he used it.
Do any readers have any other quotations whose origins they would like me to attempt to trace?