Mark Twain

...once wrote a very short story — just over 1,300 words in Twain's characteristically plain and easy style, it takes less than 10 minutes to read even at a leisurely pace. The story is, like most of Twain's stories, about the strange way in which people get along (or don't get along) with one another. But it managed to get into some touchy subjects, and Twain — fearing that reaction to the tale might limit his ability as an author to provide for his family — refused to publish it. He said "Only dead men can tell the truth in this world. It can be published after I am dead."

The story is here. The Wikipedia article is here. An animated version released this Memorial Day is here (but I must warn that it takes longer to watch than the tale does to read; I'd read first, and then watch if you're interested).