I read this interesting stuff about the history of meditation in the yoga journal:

Meditation was probably discovered by protohumans in archaic times, notes Sanskrit scholar Willard Johnson, author of the meditation history Riding the Ox Home (Beacon, 1986). Johnson suggests early humans may have stumbled upon meditation shortly after they domesticated fire and began using it for central heating. Huddling close to their bonfires for warmth, they probably spent hours staring at the hypnotic flames. At some point, they would have noticed that doing so could produce an altered state of consciousness. Johnson guesses that archaic folks might have also noticed that certain plants, sexual orgasm, physical trauma, and near-death experiences produced unusual states of mind and invented meditative techniques to recreate them. Alternatively, poet and essayist Gary Snyder has speculated that meditation may have been developed by the earliest hunters. Without bows or other long-range weapons to bring down their prey, hunters might have trained themselves to quiet their minds so they could stalk wary animals.

Records of meditation as a discipline for lay people, as opposed to priests, first show up about 500 B.C. in both India and China. The first lay meditators in India came from that culture's Woodstock generation, who rebelled against the priests' monopoly over cosmic communion and created what we know as Buddhism and Hinduism. They may have been trying to replicate the soma ecstasies of India's Vedic age, just as the 1960s flower children adopted meditation as a natural high.

About 200 A.D. the Indian author Patanjali wrote his Yoga Sutra, summarizing for mass consumption the "science of yoga." He did such a thorough job that the Yoga Sutra remains the primary source on the subject today. Contrary to what many yoga students believe, his text said little about hatha yoga postures, which weren't a widespread practice at the time. He defined yoga as "the (temporary) stoppage of the waves of the mind" (Johnson's translation). The direct route to this stoppage, he wrote, is regular meditation. The asanas described in his sutras referred to meditation postures, by which Patanjali meant anything that was relaxing and stable for both body and mind.