Genesis ( was Madame Bovary born of the same seed?) (hat-tip A.W Raitt)
-In 1836, in a teenage tale Rage et impuissance, he refers to an old maidservant in these terms: "Et la vieille Berthe se retraçait ainsi toute sa vie, qui s'était passée monotone et uniforme dans son village et qui, dans un cercle si étroit, avait eu aussi ses passions, ses angoisses et ses douleurs." (is this last sentence not particularly reminscent of @594-602 ?)
-In 1850 (or 1849), Flaubert talks about the story of a young girl who dies a virgin and in a state of mysticism, and says that the story will turn around earthly and mystical love: "ils sont réunis dans la même personne, et l'un mène à l'autre, seulement mon héroine crève de masturbation religieuses après avoir exercé la masturbation digitale"
(Lettre à Louis Bouilhet, 14 nov 1850)
(See here for a comparison of Madame Bovary and Un Coeur Simple : http://flaubert.univ-rouen.fr/etudes/prentkigb.php )
-Later, Flaubert began a plan called Perroquet which in scant detail relates the relationship between Felicité and the parrot. During the last scene, Felicity says to the priest that the chains she hears ( @11063-11073 ) remind her of the parrot's own chains (_1, IV, pp.431-32. Date unknown)
-The biggest motor for its creation, however, appears to be George Sands challenge that he should not take virtue for granted within literature and that he himself should give it an ambassador in one of his characters instead of constantly mocking (63, p519). Flaubert's response was simply to announce the creation of Un Coeur Simple!
Love: Felicity's "Besoin d'aimer" (1, IV, p.447)