Here be dragons

It a common joke that back in earlier times, ignorant mapmakers would write the words “Here be dragons” on regions of their maps that weren’t explored. Is there any truth to this? Did those words ever appear on any actual map? If so, are we certain that the original mapmaker who wrote it didn’t actually intend it as a joke?

In the Middle Ages it was apparently not unusual for maps to show pictures of dragons or dragon-like creatures in pagan regions, but there are no historical maps using the phrase in English. There is exactly one globe using the phrase in Latin (hc sunt dracones*). It is the Lenox Globe (early 16th century).

One of the also-rans is the Borgia map (15th cen.) part of the text of which says