https://en.wikipedia.org/wiki/Maria_Anna_of_Spain#/media/File:Juan_Pantoja_de_la_Cruz_006.jpg
what is this baby holding in its right hand?
and why?!
The squeamish should not click on your link, and certainly should not zoom in on the picture. The child appears to be holding the human baby equivalent of a "lucky rabbit's foot" on a chain, though in this case it appears to be a bright red "forepaw".
Or perhaps it's just an early "pacifier".