Swinston was accompanied in the box only by a mattress, pillow, her glasses and a jug of water, the New York Post reported.
"I feel bad for her. It's physically demanding. Is she just nocturnal for a month?" said one MoMA visitor, Ethan Fuirst, 17, of Manhattan.
"I think because I know more about art I'm not that interested. But maybe it's good she's using her celebrity to make people think," said another viewer, Gaby Shorr, 24, of Brooklyn, who works for an art appraiser
This isn't the first time Swinton has performed "The Maybe"; the piece was first shown in London in 1995 and then Rome in 1996.
"Those who find it chance upon it for themselves, live and in real -- shared -- time: Now we see it, now we don't," MoMA said about Swinton's piece.
2014: The Year in Music [PHOTOS]