I hit the web trying to find a quotation said by John F. Kennedy about Thomas Jefferson while entertaining a group of Nobel Laureates. This is what I found:
"the White House hasn't seen this concentration of sheer human genius since Thomas Jefferson dined here...alone."
"Never before has this room contained so much genius - at least since Thomas Jefferson dined alone."
"This much genius has not been in the White House ever since Thomas Jefferson dined alone."
"This is the most extraordinary collection of talent, of human knowledge, that has ever been gathered together at the White House with the possible exception of when Thomas Jefferson dined alone."
"There hasn't been such an extraordinary collection of talent and knowledge gathered in this room since Thomas Jefferson dined here alone."
"Ladies and gentlemen, I believe that this is the widest gathering of talent that the White House has ever seen since Thomas Jefferson dined alone."
...he remarked that his distinguished guests at that dinner included "the most extraordinary collection of talents...that has ever gathered together at the White House since Thomas Jefferson dined alone!"
President Kennedy commented that this was the greatest collection of intellects at the White House since Jefferson had dined there alone.
...he told a gathering of American Nobel Prize winners that they were the greatest assemblage of talent in the White House since Thomas Jefferson dined there alone.
I'm surprised that something as recent as this is misquoted so often. I'm partial to the first attribution since "concentration" makes more sense than "collection," "gathering" and "assemblage."
However, what did John F. Kennedy say about Thomas Jefferson?
"The most extraordinary/greatest/widest collection/concentration/gathering/assemblage of talent/genius/knowledge/intellects..."