Sweating Silver Vault    (April Fool's Day - 1896)

Hundreds of people gathered outside the New York Sub-Treasury vault, located on Pine Street, due to a rumor (spread by an unknown prankster) that the vault was "sweating" because of the warm weather, causing the silver contained inside it to exude through the marble walls. Specks of mica were pointed out in the walls to prove the theory. [New York Times, Apr 2, 1896.]