Secundinus, an otherwise unknown Manichaean auditor in Rome, wrote a letter to Augustine of Hippo (probably shortly after 404) hoping to convert him to Manichaeism. The ¶ letter, one of the original Latin sources for Manichaeism, was preserved in Augustine’s works along with Augustine’s response.
Works: CPL 324 = 725
CSEL 25, 891–901
On Secundinus: J. van Oort, “Secundini Manichaei Epistula,” in: idem et al., eds., Augustine and Manichaeism in the Latin West, NHMS 49, 2001, 161–173 (bibl.).