It's worth remembering that what we're looking for is not just people who contributed to multiple fields but generalists/rationalists: people who took a "big picture" view. (I'm willing to set aside the matter of whether their specific achievements were related to their "big picture" view of things since it will probably just lead to argument without resolution.) Leibniz would definitely fall into that category, for example, but I'm not sure Newton would. He had interests outside of physics (religion/mysticism) but they weren't really related to one another.