The first chest is at the very beginning of the chapter.
Climb onto the fountain , jump over onto the tree and climb up over it. You will spot the chest on the right.
The next one is hidden in the cave. Climb down to the very bottom and pass by the opponent guarding it. You can either fight him or blind him with Igniculus.
In this chest, there is Magic Potion
You can obtain the third and the fourth chest right after you have obtained the ability to fly. They are at two opposite ends of this location.
Fly up to the very top of the location to obtain more items. Of course, smash it with Igniculus.
If you move closer to the right wall, you will find another collectible. You have to reach out for it with Igniculus.