Fortunately, we have fairly substantial evidence that Poe may have read a work by Reverend Joel Tyler Headley titled Letters from Italy (1845) in which Headley recounts an incident eerily similar to the central event of "The Cask of Amontillado," and, more important, facts suggest that Poe read parts or the whole of Letters from Italy. We know, for example, that one of Reverend Headley's Letters appeared in The Columbian Magazine in August, 1844, which also printed Poe's article "Mesmeric Revelation," and that Poe sent copies of this issue to at two friends.
Reverend Headley's account of an incident in San Giovanni, Italy, includes a victim, from the aristocratic class, being walled-up alive--later, dying of suffocation--for some transgression against a group of men who were also aristocrats. The original account in Letters from Italyindicates that, as the victim was almost covered up in the wall, "a stifled groan . . . and all was over."
That Headley's account inspired Poe is evident in the plot elements of "The Cask of Amontillado"--both Montresor and Fortunato are part of the aristocracy; one man has seriously offended the other; the punishment consists of being walled up in Montresor's catacombs; and the last thing Fortunato does is quietly jingle the bells on his jester's costume as he gives up all hope that Montresor will relent, very similar to the "stifled groan" in Headley's account.
The significant difference between the two is that Headley's account is straight-forward and unimaginative and lacks the gothic plot elements--the luring of Fortunato into the catacombs; getting Fortunato drunk; the fact that the Montresor family motto is about revenge--all of which create a sense of doom in Poe's story.