Every once in a while I stumble upon a scientific book or article with a «motto», that is, a brief aphorism or short humorous stanza at the beginning, usually separated by its layout from the body of the text. In a book, this can also be in front of each chapter.
But is it generally considered appropriate for scientific texts or rather not advisable? In particular, does it come across as pretentious (aphorism) or frivolous (humor)? Clearly, I am unsure how to evaluate it.