The nymphs are possibly inspired from Dante manuscripts

[eggyk]

Imo, if there was to be any smoking gun that exists within digital libraries, it would be one of the circular astrological diagrams. There are plenty of weird and unique diagrams similar in their weirdness found in a wide range of manuscripts, and it is entirely conceivable that due to those works being written in known languages that they do not raise a red flag for being mysterious.  They are simply marked as something like "astronomical diagram to track phases of moon(?)" and then moved on from. 

As for nymphs, a smoking gun would have to be a drawing matching an entire scene: matching the amount of nymphs, their body positions, the things they hold, as well as the same buckets, baths or pipes. But that would be much more likely to have been spotted already, I would think.