“From the fifth century come two spectacular depictions of baptism in Ravenna. Bishop Neon added the impressive mosaic decoration to the Baptistery of the Orthodox in Ravenna in the mid-fifth century. The central disc of the dome, directly above the baptismal font, represents the baptism of Jesus, Who is full sized and stands in water to His waist, flanked to the left by John on the shore and to the right by a personification of the Jordan as a river god. Unfortunately a restoration in the nineteenth century introduced questionable elements, including the heads of John and Jesus, the top of John’s staff, AND the right hand of John holding a patera over the head of Jesus. In such cases the restorer was accustomed to an aspersion and no longer understood the significance of the hand on the head.” (pg. 129, Baptism and the Early Church)
It seems that when restoration work was done in the late 19th century, the artist hired to do this, a man name Felice Kibel, took creative license in adding things, like the patera:
” The dish that St. John is using to pour the water was added in the 19th century by a Roman artisan named Felice Kibel, who was charged with restoring the mosaics and went overboard with creative license.”
In other words, when Kibel did the restoration in the 1800s, he was mistaken in adding the patera (or baptismal dish). This was because he was used to seeing those things in RC baptisms, and super imposed the idea upon the ancient and medieval world. The first image is the Neonian image as Kibel restored it (really, he restored the top, including the head and hands). As noted,, people had forgotten that the hand was placed on the head for Baptism. I will give two additional images from the first millenial West to illustrate this practice of the hand on the head.
This is from the Benedictional of St. Aethelwold:
This additional image is from an Ottonian book of the 10th century:
The Arian Baptistry in Ravenna (which was later taken over by the Orthodox after the Lombards became Orthodox around 700), has a depiction which is undoubtedly what the original of the Neonian looked like in terms of the hand of St. John on Christ’s Head. The iconography there was never badly damaged.
The command to Baptize by Triple Immersion was oft repeated, lest by sloth or laziness the clergy ever, relying on some exception or economy [such as the so-called ‘baptism of clinics’] would state, “This is alone sufficient.”