From the upcoming book on female orgasm by Belgian writer Elisa Brune:
The Rolls Royce of sex toys is a machine that defies imagination. Did you think that you would masturbate lying down? No, you will need to sit back up and mount it. Did you think that the penetrating part would make coital back and forth movements? Not at all, it will move like no penis ever has.
You really had to think of it, and one asks oneself again how the inventor could have imagined such a thing. Through trial and error, they say, having noticed that back and forth motions generally didn’t have any effect, and that the greatest probability for a woman to have an orgasm during sex came from her taking the active position (mounting her partner) and proceeding to rock her pubis without the up and down movement. When she rocks her pubis back and forth without any up and down movements, she discovers two advantages: firstly, the clitoris stays in constant contact with her partners pubis and can therefore be stimulated and secondly the penis a completely different type of stimulation in her vagina, not through movement, but rather through pressure on her vaginal walls that she can modulate herself. Depending on whether she rocks gently or hard, slowly or fast, upright or bent over, the head of the penis will give her different sensations, amongst which she can discover which feels the best – in other words, which stimulates her G-spot. It’s the best way to identify and develop internal sensitivity. That is for practice in a couple. But how can you reproduce these advantages with a sex toy? This is where the brilliant idea comes in. What is required is a dildo that once inserted, does not slide in the axis of the vagina but stays constantly inserted, “presses” in a variable manner on the front wall of the vagina, where the G-spot is located. How though? It is of biblical simplicity: its extremity rotates.