Daguerreotype
Invented by Louis-Jacques-Mandé Daguerre and introduced worldwide in 1839, daguerreotype was almost completely superseded by 1860 with new, less expensive processes yielding more readily viewable images. In the late 20th century, there was a revival of daguerreotypy by a small number of photographers interested in making artistic use of early photographic processes.
Robert Cornelius
With his own knowledge of chemistry and metallurgy, as well as the help of chemist Paul Beck Goddard, Cornelius attempted to perfect the daguerreotype. Around October 1839, at age thirty, Cornelius took a self-portrait outside of the family store. The daguerreotype produced is an off-center portrait of a man with crossed arms and tousled hair. While Daguerre's photograph of the Boulevard du Temple, taken one year earlier, has since been discovered to incidentally include two human figures on the sidewalk (they just happened to stay motionless long enough to imprint on the exposure), Cornelius' image – which required him to sit motionless for 10 to 15 minutes – is the oldest known intentional photographic portrait/self-portrait of a human.