just have iron man put on the suit and whack the jar with a sledgehammer that has a like.. a foam outside so the jar doesn't break but it still puts enough force horizontally to pop out from under. Perhaps also chisel into the wood a little bit and oil it so you can force it horizontally faster than the hammer is pulled toward the ground.
or just break half the jar and pooh bear it.
or just break half the jar and pooh bear it.