You must never put an iron instrument into the yaw; such an application would be certain death. In order to open the yaw, you take iron rust reduced to an impalpable powder, and passed through a fine search; you afterwards mix that powder with citron juice [i.e. citrus fruit] till it be of the consistence of an ointment, which you spread upon a linen cloth greased with hog’s grease, or fresh lard without salt, for want of a better. You lay the plastier upon the yaw, and renew it evening and morning, which will open the yaw in a very short time without any incision.

The opening being once made, you take about the bulk of a goose’s egg of hog’s lard without salt, in which you incorporate about an ounce of good terebinthine [i.e. turpentine]; after which take a quantity of powdered verdigris [green dust formed of copper], and soak it half a day in good vinegar, which you must then pour off gently with all the scum that floats at top. Drop a cloth all over with the verdigris that remains, and upon that apply your last ointment. All these operations are performed without the assistance of fire. The whole ointment being well mixed with a spatula, you dress the yaw with it; after that put your negro into a copious sweat, and he will be cured. Take special care that your surgeon uses no mercurial [mercury] medicine, as I have seen; for that will occasion the death of the patient…
(Du Pratz 1774 [Tregle 2004]).