Pp. 639-641 in Annalen der Physik, Vierte Folge, Band 18. Whole volume offered. (8vo) 8¼x5½, quarter morocco, spine lettered in gilt. First Appearance, Journal Issue.

One of Einstein's rarest articles. "A few months after first publishing the theory of relativity, Einstein discovered something that particularly intrigued him; the relation between inertial mass and energy...Einstein argued that, as a consequence of the relativity principle, inertial mass is associated with all forms of energy. He was only able to establish this result for a process involving the emission of electromagnetic radiation by a system, but argued that the result is independent of the mechanism by which the system loses energy. In addition, he was only able to show that a change in energy is associated with a change in inertial mass equal to the change in energy divided by c-squared." (Satchel, Einstein's Miraculous Year, pp.117-18.) This is considered the first important step towards Einstein's formula that energy is equal to mass times the speed of light squared.