Mix 1/2 cup powdered rottenstone with 1/8 cup linseed oil, or enough oil to make a paste the consistency of peanut butter.
Rub the paste on the cracked surface with a clean cloth and gently rub it. The light abrasive action may remove enough of the top layer of shellac or varnish to repair the damage.
Wipe the paste off with a clean cloth and discard.
Apply paint thinner to a cloth and rub it across the damaged area to remove any oils, dirt or cracked finish.
Paint a thin layer of sealer on the surface. Use the same kind of sealer as found on the table. Most modern tables are sealed with polyurethane, although older pieces may have a penetrating oil, varnish or shellac finish. Wait at least 24 hours for the finish to dry completely.
Rub the area lightly with a piece of fine steel wool. Apply a dime-size amount of paste wax to the surface with a clean cloth and rub to buff it.