bathing illustrations and ritual purification

[MarcoP]

I'm surprised nobody has yet suggested that the object, held in the hand of the nymph who gets her head or eye "treated", could be her diadem.

Hello Rene,
I had not though of it, but that would be a very simple explanation!

Another possibility could maybe be that she is holding a round cup (like this from Brussels Bibliothèque Royale, Ms.5) partially submerged in the water? (the Brussels scene is a baptism, but interpreting the object as a cup obviously suggests something different: just bathing)