That quotation is a probable fabrication -- it's certainly not in any translation I've ever seen.
An hypothesis is always more believable than the truth, for it has been tailored to resemble our ideas of truth whereas the truth is just its own clumsy self. Ergo, never discover the truth when an hypothesis will do. Nicoli Machiavelli [SIC] as quoted by Professor John D. Isaacs, Chair, SCCWRP Scientific Consulting Board, 1969-1980, in testimony before the U.S. Congress, 1978 (Isaacs 1978). This tongue-in-cheek usage of a Renaissance quote, scrawled across the blackboard of a smoke-filled conference room...[SNIP]
Here's a source to "The Prince": http://www.constitution.org/mac/prince00.htm I agree, it's difficult to ascribe this quote to Machiavelli's "The Prince".