What story did Atticus tell the kids about their family history that Aunt A. was mad about?

Atticus told the story about Josh Finch, and how Josh went insane at the University.

Jem examined the small volume. “Is this the Cousin Joshua who was locked up for so long?”
Aunt Alexandra said, “How did you know that?”
“Why, Atticus said he went round the bend at the University. Said he tried to shoot the president. Said Cousin Joshua said he wasn’t anything but a sewer inspector and tried to shoot him with an old flintlock pistol, only it just blew up in his hand. Atticus said it cost the family five hundred dollars to get him out of that one—”