“Things man was not meant to know”?
Peter told me at one point about watching science fiction movies when he was a kid; he said they all tended to end with the scientist character taking off his horn-rimmed glasses, facing the camera, and intoning: "There are some things man is not meant to know."
This appears to be a deeply rooted image; Rick Kleffel gave a very similar description at the beginning of a 2002 installment of his Agony Column, for example. And related lines in the IMDB pop up in places as diverse as The Andy Griffith Show ("there are some things beyond the ken of mortal man that shouldn't be tampered with") and the 1995 video game The Dig ("There are some things Man was not meant to understand"). Not to mention an article about H. P. Lovecraft that we ran in 2001.
But I'm not seeing any specific source for the line. Was it really a common one in old SF movies, or is there some particular canonical place that used it?