Ben Wa Balls, Japan, 500 CE
One ball is hollow, the other is partially filled with mercury. The empty ball is inserted well into the vagina, the globe with mercury follows. The woman then lies down, or better yet, rocks in a chair. As she gently rolls her hips, the mercury slides back and forth in the other ball, constantly nudging the inner ball against the cervix. The vibrations are transmitted outward to the entire vagina, clitoris, labia, and inward to the uterus itself. Sometimes Japanese women continue these movements for hours, drifting from one orgasm to another.