“Did you hear about the constipated mathematician? He worked it out with a pencil”

Mathematicians solve problems with a pencil and paper. A popular joke is:
 
“Did you hear about the constipated mathematician? He worked it out with a pencil.”
 
The joke has been cited in print since at least 1992. It’s frequently added that the constipated mathematician used a “number two” pencil.
 
 
Google Groups: rec.humor
constipated Mathematician
Jay Todd Irwin
1/6/92
Did you hear about the constipated Mathematician??
He worked it out with a pencil.
 
Google Books
Vampire’s Kiss
By William Hill
New York, NY: Windsor Publishing Company
1994
Pg. 211:
It would all work its way out in the end, like the constipated mathematician and his pencil.
 
Google Groups: alt.tasteless.jokes
That constipated mathematician…
.(JavaScript must be enabled to view this email address)
1/8/94
...“worked it out with his slide-rule” in _my_ day. The modern equivalent would be ...“worked it out with his calculator”, which conjures images too fierce to imagine. So I guess it’s back to “paper and pencil”, as posted earlier. Doesn’t have the same “ring” to it, though.
 
26 February 2000, The Guardian (UK), Weekend, pg. 70, col. 5:
TELL US A JOKE…
Susan Waltham, Brightlingsea, Essex
‘Q: What did the constipated mathematician do?
A: Work it out with a pencil.’
 
Google Books
Monologues for Show-Offs
By Donna Daley and Julie Halston
Portsmouth, NH: Heinemann
2008
Pg. 114:
What did the constipated mathematician do? He worked it out with a pencil. Sorry. Do you think he used a number two pencil? Sorry. Sorry if I went off on a tangent.
 
Twitter
Duncan Robertson
‏@whomwah
Did you hear about the constipated mathematician that worked it out with a pencil?
7:42 AM - 12 Aug 2008
   
24 August 2008, Washington (DC) Post, “Questioning Authority” by Gene Weingarten, pg. W32:
Did you hear about the constipated mathematician? He worked it out with a pencil!
 
Twitter
jarredpoor
‏@jarredpoor
Did you hear about the constipated mathematician? He worked it out with a pencil, it was a number 2
9:20 AM - 14 Jul 2012
 
reddit
Did you hear about the constipated mathematician? (self.Jokes)
submitted May 7, 2013 by N8_erade
He worked it out with a pencil.
 
YouTube
Math Jokes Explained - Numberphile
Numberphile
Published on May 20, 2013
Some of your favourite maths jokes are dissected in forensic fashion.
6:28
“Did you hear the one about the constipated mathematician? He worked it out with a pencil?”