Wasn’t the diner a drive system for some ship in one of the Hitchhiker’s Guide to the Galaxy books?

Yup. It was from Douglas Adam’s *Life, The Universe, and Everything*:

Bistromathics:

The most powerful computational force known to parascience. Bistromathics is a way of understanding the behavior of numbers. Just as Einstein observed that space was not an absolute, but depended on the observer’s movement in time, so it was realized that numbers are not absolute, but depend on the observer’s movement in restaurants.

The first nonabsolute number is the number of people for whom the table is reserved. This will vary during the course of the first three telephone calls to the restaurant, and then bear no apparent relation to the number of people who actually turn up, or to the number of people who subsequently join them after the show/match/party/gig, or to the number of people who leave when they see who else has turned up.

The second nonabsolute number is the given time of arrival, which is now known to be one of those most bizarre of mathematical concepts, a recipriversexclusion, a number whose existence can only be defined as being anything other than itself. In other words, the given time or arrival is the one moment of time at which it is impossible that any member of the party will arrive. Recipriversexclusions now play a vital part in many branches of math, including statistics and accountancy and also form the basic equations used to engineer the Somebody Else’s Problem field.

The third and most mysterious piece of nonabsoluteness of all lies in the relationship between the number of items on the check, the cost of each item, the number of people at the table and what they are each prepared to pay for. (The number of people who have actually brought any money is only a subphenomenon in this field.)

Numbers written on restaurant checks within the confines of restaurants do not follow the same mathematical laws as numbers written on any other pieces of paper in any other parts of the Universe…