Place a clean, thick piece of cloth on the area with the water mark. You can use an old cloth diaper, an old cotton T-shirt or even a hand towel.
Set your iron on a medium heat setting; it should be warm but not hot, according to the University of Georgia.
Iron the spot for a few seconds, just enough to effectively warm the fabric. Repeat the ironing step for short periods until the mark is gone.
Place a generous amount of mayonnaise or another oily substance such as petroleum jelly onto the water mark.
Rub the area with a paper towel or soft cloth. Leave the mayonnaise or petroleum jelly on the stain overnight.
Rub the area again with a paper towel or cloth for approximately 20 minutes to remove the stain. Remove all the residue with a clean cloth.
Wax the furniture as usual; the water mark or ring should be gone.