Note from Piero is a written note found in Dishonored.
Corvo, thank you for getting me a live weeper. This is going to be invaluable for my old friend at the Academy of Natural Philosophy, as living plague specimens are quite difficult to procure. Rest assured my colleague will handle this situation as humanely as possible.
It can be found any time after the mission House of Please, stuck to a wall in Corvo Attano's bedroom with sleep darts. It is only available if at least one of the weepers in the sewers beneath the Hound Pits Pub was knocked unconscious before the mission House of Pleasure.