Ran across this quote in a book I was reading recently. It was supposedly said by Isaac Newton in response the South Sea Bubble.
I can calculate the motions of the heavenly bodies, but not the madness of people.
Wikiquote lists the quote as disputed. It appears to have been a statement made about Newton (“[he] could calculate the motions of erratic bodies, but not the madness of a multitude”) that later was transformed into a statement by him.
Still, a sentiment that rings true regardless of who said it.