Newton hid Calculus in letter: The Fundamental Anagram of Calculus (see here: www.mathpages.com/home/kmath414/kmath414.htm)   Here's an interesting quote from the correspondence of Isaac Newton:      This is from the 2nd letter that Newton wrote to Leibniz (via Oldenburg) in 1677. He was responding to some questions from Leibniz about his method of infinite series and came close to revealing his "fluxional method" (i.e., calculus), but then decided to conceal it in the form of an anagram