Ermine and Weasel
The ancient Zoroastrians, however, considered ermines sacred because their white coat was a symbol of purity.
The Bundahishn, an old Zoroastrian text, states that ermine is the chief of all fur animals.
Ermines are holy because they had once joined the assembly of the Amesha Spentas (Chapter 14/24).
The ancient Zoroastrians appreciated ermines because they could hunt rats, squirrels and other rodents.
There are many different kinds of ermines and weasels, and they are all scattered around the world
from Asia to Northern America to New Zealand. The Bundahishn names eight different species of the ermine. Today we know there are at least 37 species of the ermine.
One is called Fergana Stoat and it is native to India and Afghanistan. The Fergana Stoat has a short and soft grayish coat and sometimes light spots form a collar on its neck. This stoat never turns white in winter.
Like ancient Zoroastrians, some Europeans considered an ermine a symbol of purity. They believed that an ermine will choose to die rather than make its white coat dirty.
Leonardo wanted to show the purity of Cecilia by painting her with a white ermine in her hand.