Note: The Jackanism move is obtained on the second level, so you will not be able to get this chest on your first play of the level.
Open the Jackanism* chest in the Prison Fortress level.
*To activate Jackanism: hit RT,LT, and A at the same time.
You will not be able to access this just the first time playing through the level, you must replay the level, when you do there will be 3 shrunken heads right next to the chest for you to use.
The chest is right behind the little staircase next to you when the level starts.