A big box of bison bladders, similar to the kind George Catlin used to store his paints.
If his brush stroke doesn't tip you off, his subject matter will. And if by the subject matter you can't tell that George Catlin's paintings were done in the field, then seeing his buffalo bladder paint skins will put all doubt from mind.
Catlin is the subject of the "Art à la Cart" program at SAAM this weekend. In conjunction with the National Museum of the American Indian's National Powwow across the street at the Verizon Center, materials representing those that Catlin would have used to paint his naturalist works while traveling in the West will be out for you to look at and touch. One of those objects is a bison bladder—which Catlin used to store his paints.
Update: The cart will be in our galleries from 1 - 4 on Saturday, and it will be out again from 1 - 4 on Sunday if demand is high.