Process the following in a juicer or blender:
- 2 medium tomatoes, quartered (about 8 ounces)
- 2 large celery ribs, cut into chunks (about 4 ounces)
- 2 large carrots, cut into chunks (about 6 ounces)
- 4 sprigs parsley
- (½-inch piece peeled horseradish root)