The 1912 Yale Peruvian Scientific Expedition Collections from Machu Picchu Yale University Publications in Anthropology

"This synthesis of the archaeological evidence of metallurgy at Machu Picchu interprets new data on Inca metal artifacts that represent the final stage of pre-Columbian metallurgical technology in the central Andes of South America. These artifacts were recovered early in the 20th century by the Yale Univeristy Peruvian Scientific Expeditions"--