It was a Fullomyth, an invaluable aid for all whose business is with the arcane and hermetic. It contained lists of things that didn't exist and, in a very significant way, weren't important. Some of its pages could only be read after midnight, or by strange and improbable illuminations. There were descriptions of underground constellations and wines as yet unfermented. For the really up-to-the-epoch occultist, who could afford the version bound in spider skin, there was even an insert showing the London Underground with the three stations they never dare show on the public maps.