A website dedicated to documenting the history of slavery in the US quotes from slave trader turned abolitionist Thomas Branagan, who describes the iron bit through a "front and profile view of an African's head, with the mouth-piece and necklace, the hooks round which are placed to prevent an escapee when pursued in the woods, and to hinder them from laying down the head to procure rest."
An 1848 article in The North Star states that "dealing in slaves has become a large business: establishments are made in several places in Maryland, at which they are sold like cattle.
A man wrote in an open letter to the editor of the Frederick Douglass Paper about an abolitionist who was demonstrating the actions of slave holders in the American South, I recollect the horror that thrilled the hearts of the spectators, when Mr. Gurney one evening placed on his head an iron machine of torture, which inflicted great pain upon the slave, and an iron gag penetrated his mouth, confining his tongue and preventing articulation.
The description of her is given that she is "5 feet three or 4 inches high, had on, when she went away, such clothing as negroes generally wear in the summer, and carried with her a white linen coat and jacket.
Some of them were allegedly chained in uncomfortable positions and instruments of torture were said to have been found … [Specifically] iron collars with spikes or sharp edges.