When I was writing Conjurin' Ole Time: Hoodoo Spells 1800 - 1920, I kept careful track of my citations from the various libraries I visited and online resources used over the several years I spent gathering my information. Then, when I was ready to print the book -- I felt like an idiot when I discovered a few of my citations were either missing or improperly recorded! I ended up making a note in the bibliography about that matter, that there might be a few things where the citations couldn't be found... instead of having to delay the book in hopes that the might eventually be rediscovered.
I'm happy to report that today I came across the note for one of those lost citations! I had mentioned in the book that sigils had been used in African magic since at least the year 1800, but couldn't seem to find my source on that. I finally happened upon a note I scrawled down on a paper that apparently got separated from the rest of my notes -- "1800, 'A Treatise on Sugar' Benjamin Moseley - sigils."
Moseley didn't have the nicest things to say about black people or their magical practices, but here's his mention of the use of sigils:
The new printing of the book, Conjuration: Hoodoo Spells from 1800 to 1920 has amended the bibliography.