via NYPL.org’s Explore blog:
In the early eighties, rare book librarian John Rathe pulled down a dusty box, wrapped in twine, from a remote corner of the Rare Book room. Attached to the box was a label that said: “Do not open until war is over.” Which war? The Civil War? The War of 1812? What he discovered was a box filled with disguised anti-Nazi tracts hidden in packets of tea and shampoo and concealed in miniature books both popular and scholarly.
Read Jack Sherefkin’s full blog entry HERE, which discusses more about about this interesting discovery and the history behind it’s concealment.