I just had a young gentleman in the library needing more
information about the following quote attributed to Twain:

     "When I was a boy of 14, my father was so ignorant I
     could hardly stand to have the old man around.  But
     when I got to be 21, I was astonished at how much the
     old man had learned in seven years."

Three quote sources in our collection (newest one is 1988)
say the quote has never been found in his works.
The lad was looking for more context to go with this quote
for a funeral service on Saturday.  Does anyone have
any information they can share quickly?
Thank you in advance.