De Ceremoniis
From the 4th century CE the term "decanus" became used for palace messengers, particularly those in the service of Roman empresses. "Decani" also apparently served as guards at gates, and in the 6th century, John Lydus equates them with the ancient lictors. In the 899 "Klētorologion" of Philotheos, the "decanus" (transcribed into Greek as δεκανός, dekanos) was a mid-level functionary, serving under the "protasekretis". According to the mid-10th century "De Ceremoniis" of Emperor Constantine VII Porphyrogennetos (), a "decanus" was "in charge of the imperial papers" when the Byzantine emperor was on campaign.