To transfer your image onto the eraser, flip the tracing paper over and place it face down on the eraser. Rub the back of the paper with a rounded stick to burnish the design onto the eraser.
                 

You should now be able to see the image clearly on the eraser. (It will be reversed.) Trace over the image with an ink pen so it is easier to see.

If you want to experiment with a more modern technique, try making a photocopy of your image. Place it face down on your erasaer, and either:

1. wet it with acetone (nail polish remover), or

2. cover it with a cloth, and then go over it a few times with a medium/low heat clothes iron.