Lakulisha, a prominent guru c. 200 B.C
It sure looks to me like he is meditating with a hard-on. Getting turned on by meditation, by the way, one of the sweetest feelings. It happens spontaneously sometimes as a result of how relaxing and intrinsically erotic meditation is. If you just let the electricity build, the sexual charge permeates every cell of the body, enlivens the nerves and senses, and makes you feel slightly intoxicated. The electricity usually comes in waves, and the building up of the wave, the peaking, and the descent are all interesting. Sexual energy is creative energy. In meditation, it adds healing power to rejuvenative and re-create your body.
I get the feeling that for some people, "celibacy" can be a very turned-on state. One day in Majorca, on a meditation course, a young man stood up asked a question about sex, and then in the next sentence implied that Maharishi, being a monk, wouldn't know anything about the delights of being with a woman. Maharishi immediately sat up in his chair and said strongly, "You don't know what I think about!"
Khajuraho c. 1200 A.D.
Beautiful.
If you want to see what a life-affirming, male & female embracing teaching on meditation is like, check out The Radiance Sutras.