Sometimes people believe untrue things because they want them to be true, as the first chapter shows with a look at examples such as the Rosicrusians and the mythical kingdom of Prester John. But novel (if rather doubtful) ideas can provide useful insights into how information spreads around, as Eco shows in the second chapter which looks at who influenced Dante in his speculations about the original language of Adam. Likewise the third chapter looks at how the animals found in newly explored lands were interpreted in terms of existing literature -for instance the rhinocerous as a unicorn. The fourth chapter looks at attempts to create a language with the minimum of redundancy and the last chapter at the linguistics of Joseph Maistre.
To some degree these essays seem to be ones which didn't get into The Search for the Perfect Language, so they are rather a random selection of topics. I didn't find the last chapter particularly interesting, but the others did give an entertaining look at some of the obscure corners of linguistics.