Instructions
Step on the switch at the start of the "Haunted Tomb" level to open the sealed door. There is a coffin in this area, but ignore it for now. Go down the steps and head to the right. You will see a few large stone monsters that are hurling bombs at you.
Dodge the incoming bombs. Walk up to a bomb after you dodge it and you will automatically swallow it. Return to the original room with the coffin in it.
Press the "Circle" button to spit the bomb at the coffin. To aim the bomb more precisely hold down the "Triangle" button and move the target icon with the directional pad before pressing "Circle" to fire. Repeat this process to destroy all coffins in this level.