One of my teachers of French once told an anecdote about Gustave Flaubert in class. I'm not certain I remember all the details correctly, so what follows is how I remember, or possibly misremember after more than 25 years, the story.
Flaubert was staying in (presumably) a hotel and was writing or improving a draft of one of his works. When he had finished a chapter or a section, he read it aloud. As the window of his room was open, passers-by on the street stopped to listen to the story. When Flaubert stopped reading, he noticed that a small crowd had gathered near the window.
That Flaubert worked very intensely on improving his style and that he loved to read aloud are no secrets. For example, James Wood writes in How Fiction Works,
Flaubert loved to read aloud. It took him thirty-two hours to read his over-blown lyrical fantasia The Temptation of Saint Anthony to two friends. And when he dined in Paris at the Goncourts, he loved to read out examples of bad writing. Turgenev said that he knew of 'no other writer who scrupled in quite that way'. Even Henry James, the master stylist, was somewhat appalled by the religious devotion with which Flaubert assassinated repetition, unwanted clichés, unwanted sonorities. The scene of his writing has become notorious: the study at Croisset, the slow river outside the window (...)
I have quoted the above passage so extensively because it might contain clues about the correct version of the story I tried to reproduce from memory: perhaps the story was reported to one of the friends or authors mentioned above, perhaps it can be found in their or Flaubert's correspondence or other biographical writings, and perhaps Flaubert was not staying in a hotel after all.
In spite of my efforts, I have not been able to find the anecdote in sources I could find online. I would be grateful if someone could find its source and, if that information is available, the title of the work that Flaubert was writing at that time.