Back-of-the-Envelope Calculation

It was from Kuiper that I first got a feeling for what is called a back-of-the-envelope calculation: a possible explanation to a problem occurs to you, you pull out an old envelope, appeal to your knowledge of fundamental physics, scribble a few approximate equations on the envelope, substitute in likely numerical values, and see if your answer comes anywhere near explaining your problem. If not, you look for a different explanation. It cut through nonsense like a knife through butter.

 Oulipo - "workshop of potential literature"

Finally elaborated, this definition remains the Oulipo's rule. In his conversations with Charbonnier, Queneau returns to it nearly word for word: The word "potential" concerns the very nature of literature; that is, fundamentally it's less a question of literature strictly speaking than of supplying forms for the good use one can make of literature. We call potential literature the search for new forms and structures that may be used by writers in any way they see fit. Finally, and more recen...