Yeah, unfortunately that little chest is not reachable by any normal means. I think you CAN use the Ctrl-J teleport cheat with the console enabled to teleport down there though. As butteredsoul mentions though, all the crate contains is just some minor random loot.
The first time I Ctrl-J'd over to it I was so excited. I thought it was a chest the devs made that you'd have to use Dimension Door to get to (and then decided against having that spell in the game). Imagine my disappointment when I found it contained 6 gold pieces. Haven't bothered to jump over to it again after that.
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Reference: http://forums.pocketplane.net/index.php?topic=19566.0