In 1710 he edited the "Liber ad Donatum confessorem de mortibus persecutorum", and in a special dissertation tries hard to prove that the book was written by Lucius Caecilius and not by Lactantius.
Lactantius describes that sign as a "staurogram", or a Latin cross with its upper end rounded in a P-like fashion.
Lactantius Placidus (350–400 AD) was the presumed author of a commentary on Statius's poem Thebaid.