Well, I had tried to puzzle this out when I did the first post, but I was stumped! I tried again today, looking at the largest scan available for this image from the City of God manuscript but I was not able to puzzle out the Latin banner above the boys in the furnace. Maybe someone with more discerning eyes will be able to figure that out! Here is the largest view available - can anybody read what it says on the banner?
Meanwhile, in order to scrounge up the largest view I could find of that image, I visited the other images at the Dutch National Library that show the boys in the furnace. Here they are!
Here is an illustration from a beautiful Bible historiale, circa 1372.
In a much more simple style, here is an illustration from a Speculum humanae salvationis manuscript dated to the 15th century:
And here is a very dramatic illustration from another Speculum humanae salvationis, circa 1450:
