His mouth was such a post-office of a mouth that he had a mechanical appearance of smiling. We had got to the top of Holborn Hill before I knew that it was merely a mechanical appearance, and that he was not smiling at all.
– Charles Dickens
Great Expectations, Chapter 21. Dickens uses a unique metaphor to humorously describe one of the features of his character’s face. In the book Wemmick’s mouth is compared to a post-office, emphasizing the rigidly controlled and unemotional nature to his character. Wemmick is clerk to the lawyer Jaggers.