The talk of a magic box reminded me of the ‘eternity’ passage from the Third Policeman.
Don’t read this if you want to read the Third Policeman! I’ve condensed the relevant parts:
[spoiler]…The narrator is led, by a policeman, into a vast underground network of rooms beneath the real world …
‘Is this eternity?’ I asked. ‘Why do you call it eternity’?
‘Feel my chin,’ MacCruiskeen said, smiling enigmatically.
‘We call it that,’ the Sergeant explained, ‘because you don’t grow old here. When you leave here you will be the same age as you were coming in and the same stature and latitude. There is an eight-day clock here with a patent balanced action but it never goes.’
‘How big is all this place?’
‘It has no size at all,’ the Sergeant explained, ‘because there is no difference anywhere in it and we have no conception of the extent of its unchanging coequality.’
…
‘Could you not bring your bicycle and ride through all of it and see it all and draw a chart?’ I asked.
The Sergeant smiled at me as if I were a baby.
‘The bicycle is easy,’ he said.
To my astonishment he went over to one of the bigger ovens, manipulated some knobs, pulled open the massive metal door and lifted out a brand-new bicycle.
…Now they walk out of the room and reenter the same room (to the narrators horror). The policeman then proceeds to produce shapes from the machine which the narrator cannot find words to describe…
‘What else is there?’
‘Anything’
‘Anything I mention will be shown to me?’
‘Of course’
…The narrator gets greedy, and asks for loads of stuff (i.e. whiskey, gold, a suit, etc) from the machine - which is duly given to him. Then they leave and travel through more underground rooms until they reach the way out - a lift…
The simple thing is, MacCruiskeen said calmly, 'that you cannot enter the lift unless you weight the same weight as you weighed when you weighed into it.
…So he can’t take his loot away with him…
[/spoiler]
Food for thought, anyway. Perhaps the losties cannot leave the island unless they are the same way they were when they arrived - something along those lines?