Evidence of the smoking of cannabis can be found as far back as the Neolithic age, where charred hemp seeds were found in a ritual brazier at a burial site in present day Romania[2] .

The most famous users of cannabis were the ancient Hindus. It was called ganjika in Sanskrit (ganja in modern Indian languages).[3] According to legend, Shiva, the destructive aspect of the Hindu trinity, told his disciples to revere the plant. The ancient drug soma, mentioned in the Vedas as a sacred intoxicating hallucinogen, was sometimes associated with cannabis. It has also been identified with a number of other plants and a mushroom, Amanita muscaria, so the involvement of cannabis cannot be definitively quantified.

Cannabis was also known to the Scythians, as well as to the Thracians/Dacians (ancestors of present day Eastern-Europeans), whose shamans (the kapnobatai - "those who walk on smoke/clouds") burned cannabis flowers in order to induce trances. The cult of Dionysus, which is believed to have originated in Thrace, is also believed to have inhaled cannabis smoke.
http://en.wikipedia.org/wiki/Marijuana