In such a case secrecy must be absolute to be effective, and although mere vague curiosity induced many persons of my intimate acquaintance to ask to be allowed to just go in and have a peep, I never admitted anyone.
Henry Bessemer: Making Steel From Iron (Uncharted, Unexplored, and Unexplained) (Uncharted, Unexplored, and Unexplained: Scientific Advancements of the 19th Century)