William H. Pickering, "A Method of Measuring the Absolute Sensitiveness of Photographic Dry Plates".

Offprint, Proceedings of the American Academy of Arts and Sciences, pp 159-162. 

• Paper a bit fragile at the edges; also, there's an old vertical fold through the publication.  Good copy, only, though it is signed by Pickering.  
• Signed "with the compliments of / the author"

"[Pickering] graduated from Massachusetts Institute of Technology in 1879. He taught there for a time and was appointed an assistant professor at Harvard observatory in 1887. In 1891 he set up Harvard’s Boyden Station at Arequipa, Peru. Around 1900 he led expeditions to Jamaica, and from 1911 he was in charge of a permanent Harvard observing station here. Upon his retirement in 1924 the station became Pickering’s private observatory. Pickering was a pioneer in dry-plate celestial photography, and the Harvard photographic sky survey was undertaken at his suggestion. He took some of the earliest photographs of Mars (1888), and the lunar photographs he obtained in Jamaica (1900) were long the finest and most complete." Dictionary of Scientific Biography