Edgar Allan Poe’s short story “The Facts in the Case of M. Valdemar” was published in 1845. In the story a “mesmerist” (a kind of hypnotist) puts a dying man called Valdemar in a suspended hypnotic state at the moment of death. The man’s body becomes cold and inert. It is left for months. Finally the narrator wakes him. Valdemar shouts “dead! dead!” before decaying into a “nearly liquid mass of loathsome—of detestable putrescence.”
Earlier in the story, when Valdemar is about to die, the narrator says: “I now feel that I have reached a point of this narrative at which every reader will be startled into… disbelief. It is my business, however, simply to proceed.”
I take that as Poe saying it is his “business” as a writer to let his gruesome and fantastical imagination take us out of realism into an altogether different realm.
Some contemporaries felt this kind of writing was silly. William Simms wrote that Poe’s “genius was rather curious than valuable- bizarre rather than great or healthful.”
The idea that “genre” writing is curious rather than valuable persists. But many readers find as much truth in it as any other kind of writing.
After all, isn’t “realism” as much of a literary construct as anything else?
You can read “The Facts in the Case of M. Valdemar” at http://www.eapoe.org/works/tales/vldmard.htm