Historic oil on canvas, contemporary inserts, lacquered wood.

Time worked for an hour of light.

1800 - 6 hours work for an hour of light
1850 - 2.5 hours work for an hour of light

1900 - 11 minutes work for an hour of light
1950 - 8 seconds work for an hour of light
2000 - 2 seconds work for an hour of light

(Source: HumanProgress.org)