| Unidentified artist Quill containing microscopic despatches fastened to a tail-feather of carrier-pigeon n.d. Book illustration Google Books LL/50999 Gaston Tissandier, A History and Handbook of Photography (London: Sampson, Low, Marston, Low and Searle / New York: Scovill Manufacturing Company, 1876), fig. 55, p. 237
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