scandinavegan says:"I'm sure Feynman read both, but I was interested in the origin of the quote, since I learned it a few days ago and think it's very inspirational."
As I continued reading I found the relevant quote to the second text, Calculus Made Easy, on page 194 of Feynman's "The Pleasure of Finding Things Out", where Feynman states:
"I had a calculus book once that said, 'What one fool can do, another can.'"
While he doesn't name it, that's almost without a doubt "Calculus Made Easy". Both calculus texts are thus referred to in Feynman's "The Pleasure of Finding Things Out". In the index of that book, under the topic "Calculus", the pages of both references can be found.
As I continued reading I found the relevant quote to the second text, Calculus Made Easy, on page 194 of Feynman's "The Pleasure of Finding Things Out", where Feynman states:
"I had a calculus book once that said, 'What one fool can do, another can.'"
While he doesn't name it, that's almost without a doubt "Calculus Made Easy". Both calculus texts are thus referred to in Feynman's "The Pleasure of Finding Things Out". In the index of that book, under the topic "Calculus", the pages of both references can be found.