I went last Wednesday with a normal sized backpack and was told to check it in.
If you carry it on one shoulder, and it is small, yes. They don't want exhibits to get accidently upended.
They say You're supposed to check them in but when I was there yesterday I also saw a lot of people with backpacks I guess it depends on what exhibit you are going to go see
I saw a number of people with bags and backpacks.
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