Susannah points us to this hard-to-find title: Gelatin – The B-Thing. Published in 2002. One copy left at Skylight Books in LA. From the publisher's notes:
"At 6 o'clock one morning, Austrian art group gelatin suctioned out a window on one of the top floors of the World Trade Center, shunted out a narrow balcony constructed of smuggled building materials, and posed on it while a helicopter flew by and took their photographs. An unbelievable, completely illegal, and fully secret stunt when it was performed, The B-Thing is now unbearably surreal, weirdly prescient, and forever unrepeatable."