There is a rarely seen etching created by Rembrandt that shows a "Rat
killer" with a ferret liked animal perched on his shoulder:

http://www.rembrandtpainting.net/rmbrndt_etchings/etchings_c/cs.htm

Rembrandt made a lot of etchings depicting life in that era of time,
it only seems fit that this "rat killer" would use a ferret to aid in
his work.

Personally, I think ferrets were trained a lot differently than what we
train our ferrets to do and sitting on the shoulders came to nature to
our weasel's relatives. However, I wouldn't picture a ferret sitting in
a certin position too long to be painted by life. For example, look at
Leonardo da Vinci's "Lady with Ermine", the muscles in his arms of
those of a person.

[Posted in FML 5865]