John Glenn's classic comment, 9 April 1959

[Kiwi]

Because the effect of spaceflight on the human body was an unkown at the time, the original seven Mercury astronauts had to go through an incredible barrage of medical tests, both for fitness and so that comparisons could be made after a flight.

On 9 April 1959 they all attended their first press conference where they were introduced to the public. There's a famous photo of all of them with their hands up in reply to one journalist who asked who really expected to return alive from space. Wally Schirra and John Glenn had both hands up.

One of the questions they were asked was, "Would the gentlemen mind telling us which one of tests they found the hardest?"

John Glenn's reply generated a lot of laughter:

"That's a real tough one because we had some pretty good tests, but I think the tests out at Dr Lovelace's place at Albuquerque out there... certainly some of the tests we had out there were the most trying. And it's rather difficult to pick one, because if you figure how many openings there are on the human body and how far you can go in any one of 'em…

"Now, you answer, which one would be the toughest for you!"

[Ginnie]

Enos the monkey even had 1300 hours of training, including 343 hours of actual capsule-couch conditions. He had a four to six hour work day, including medical tests .
I wonder if he was poked and prodded in all those places.
There were a crew of four 'backup pilots' including Ham, the first chimp (I believe) that the U.S. had put in space. Ham had only 250 hours of training for his flight.