<p>So I realise that this response is probably a bit late, but since nobody seems to understand what they're saying, I'll shed some light and explain. In the Hall of the Elements at the College of Winterhold, once you enter the main chamer immediately turn left. Once you see the first bench, that is the spot where you'll want to use the plate glitch to go through the wall behind the bench. You will fall out of bounds, and while you will see the chest, you won't be able to reach it without using the Do Not Delete chest, which can be found in a few locations (I personally grab it from The White Phial in Windhelm. It's upstairs, and you have to use the plate glitch to go through the walls to reach it.). Since the Do Not Delete chest floats in the air, it can be used as a floating platform out of bounds to reach the chest that the OP was referring to underneath the Hall of the Elements (You may want a few of them to make reaching it easier). The chest will contain quest items related to several different quests around the college, including the Sigil Stone for the Conjuration Ritual Spell and the Spell Tome version of the Power of the Elements Book for the Destruction Ritual Spell.
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