Prior to the invention of rockets, was there a phrase equivalent to: "it's not rocket science"? If so, what was it?
Here I am looking for a phrase that makes a comparison with a difficult job/task, so "easy as pie" wouldn't work. I'm also looking for a phrase that would also have been used before modern medicine. Thus, something different from, "it's not brain surgery".
To clarify: I'm looking for a phrase that was actually used in the English language. It could have been used in any English speaking country. Any time prior to when the expression "it's not brain surgery" might have been used, so earlier than probably 1930 or 40.