On wilderness camp trips my grandfather would use burlap feed sacks that
we packed the grain in with. Fold the sack in half by pulling the top
half down over the bottom half. Then slip rocks or pine cones up inside
the corners and tie twine around the rock. Use enough twine to go over
the horses head. My dad would cut the excess bag flaps off and use them
to sit on.
Hope this helps you out.