On this page of our guide to Psychonauts 2, you will find Supply Chests available in The Quarry.
Six Supply Chests can be found in this level.
Chest No. 1
Location: Otto's Laboratory.
You'll come across this chest in Otto's Laboratory. You have to jump on the wooden platform to the left of the machine with brains. Then keep moving forward, using everything along the way, until you jump to a stable platform with the chest.
Chest No. 2
Location: Motherlobe Area.
You'll find the chest right below the facility. Just jump off the edge and use levitation to get to the right place.
Chest No. 3
You'll find the chest to the left of the tree house. All you have to do is jump on the wooden platform.
Chest No. 4
Location: Lili's Garden.
You have to use a boat get to this chest. Leave it under a rock. Then you'll be able to climb up the tree without any problems.