Paper mache was a very popular material with the Victorians, who used it to make furniture such as bookcases, tables and chairs. These items were often quite elaborate, and were made with as many as 100 layers of paper. They were ornately decorated and are today prized as fine examples of the furniture-maker's art. While you yourself may not be able to scale such heights, you can make a good-looking chair that will support your weight with relative ease.
Mix your wallpaper paste with water in a bowl until it is the consistency of thick soup.
Tear your newspaper into strips of 1"x4".
Tape the ends of your cardboard tubes to the bottom of your square box, one in each corner. Then tape the edge of your rectangular box to the top of your square box, making a chair shape.
Dipping your newspaper strips into the wallpaper paste, begin to apply them to your cardboard chair, starting with the tubes and working your way upwards. Remember to overlap your strips so that there are no gaps. Apply two layers of paper to the chair.
Put the chair somewhere warm and dry overnight so that the paper mache can dry.
Apply another two layers of paper mache and leave to dry again.
Paint the chair with a white emulsion paint and leave to dry.
Decorate the chair in whatever way you wish. For a particularly-impressive "throne" look try painting it with gold or silver paint.