Isaac Newton, Upon the prophecies of Daniel.
Chap. IV. Of the vision of the four beasts

The head of the image was of Gold;
and signifies the nations of Babylonia, who reigned first,
as Daniel himself interprets :
"Thou are this head of gold," said he to Nebuchadnezzar. ...
The breast and arms of the image were of Silver;
and represent the Persians, who reigned next.
The belly and thighs of the image were of Brass;
and represent the Greeks,
who, under the dominion of Alexander the Great,
conquered the Persians, and reigned next after them.
The legs were of Iron;
and represent the Romans, who reigned next after the Greeks