The most complete medieval treatise on urinoscopy. Actuarius was first to use a graduated glass for its examination. Joannes Zacharias Actuarius was the last of the great Byzantine physicians. Actuarius or actarius (Greek: ἀκτουάριος), was a title applied to officials of varying functions in the late Roman and Byzantine empires. By 12th century, or perhaps in the 11th century, the term came to be applied to prominent physicians, possibly those attached to the imperial court. By the 16th century the title Actuarius was conflated as Joannes's last name. This is the first complete Latin translation. An abridged edition appeared in 1519. Partial English translation in No. 2241.