metalpoint styli in Rome or Greece

I've begun to research metalpoint as a drawing technique. As far as I can tell, metalpoint was not used for drawing until the Renaissance but was possibly used for writing before that. I'd like to be able to document its early uses, if possible (scribal or artistic). I've read in a number of places that various metals were used as far back "antiquity" in Rome and possibly Greece. One silverpoint site mentions the Greek poet "Thessalonika."

Can anybody help me? Point me to sources that are a bit more solid than what I've found? Names? Places? Dates?

Thanks for any help you can give me.