Hopper in ocean border cave

Does anyone know what goes in the hopper in the cave at the edge of the world at -2281, 30, -3567? I tried dynamite and the Talking Mushroom, but neither activated any mechanisms. It looks like theres a huge boulder behind it that could be moved/removed with the right item thrown in.

Lmk what yall think, or if someone has already figured this out.

 

I asked about this in the discord a few weeks ago. Apparently there used to be mobs that spawned there that dropped an item you would put inside the hopper. This would then give you access to a loot chest, but ths mobs were at some point removed.