It is interesting that you chose "Charles Ball". Obviously written by an educated person and in its preface admits...
"THE story which follows is true in every particular Responsible citizens of a neighboring State can vouch for the reality of the narrative. The language of the slave has not at all times been strictly adhered to, as a half century of bondage unfitted him for literary work The subject of the story is still a slave by the laws of this country, and it would not be wise to reveal his name."
So "Charles Ball" is not his real name.
Mark Twain comes into the "Charles Ball" story. How? He used this story one of his famous books
"In his own notes about the sources of Connecticut Yankee, Mark Twain referred to this as "Autobiography on Charles Ball." He may have first come across this early anti-slavery narrative, first published in 1837 and reprinted in 1858, in the library of his abolitionist in-laws. Ball's narrative, apparently dictated to an editor identified as "Fisher," covers forty years "as a Slave." Included here are the passages that were used most directly in the accounts of slavery in Connecticut Yankee."
So here is a book, writen and published by abolitionist, about an unnamed slave, used as a source for fiction by Mark Twain.
I love history.