Push the envelope
To push the envelope means to go beyond commonly accepted boundaries and has nothing whatsoever to do with stationery. Push the envelope is originally technical jargon from the field of aeronautics and dates from the 1940s. The envelope here is a mathematical term that describes the technical limits of an aircraft by means of a graph. Tests pilots were advised to stay within graph’s ‘envelope’ or range but would always try to extend the aircraft’s performance and so ‘push the envelope’. It was not until the 1970s that push the envelope started to enjoy its current, everyday usage as opposed to being purely aeronautical jargon.