Principia Mathematica was written by English academics Bertrand Russell and Alfred North Whitehead, and first published in 1910. The book consists almost entirely of propositional calculus, a system of symbols describing logical statements.

It was not a bestseller, and while not recommended as light reading, it is notable as a possible model for the time travellers' manual of grammar mentioned in the Hitchhiker trilogy, which, you will recall, was blank after the initial chapters. A number of works could lay claim to the title, but Principia Mathematica has a special plea: most editions appearing after the initial publication include only the first fifty-six chapters. Russel revised the book, removing much of the propositional calculus, and published it with the snappier title, The Principles of Mathematics; but again sales were slow. Perhaps we will never know what he was trying to say.