A female dominant in a master/slave relationship is often termed a Mistress, not to be confused with the colloquial usage of mistress as a kept sexual partner without a similarly formalized power relationship. The term applies to the depiction of the act rather than the act itself, and so does not include live exhibitions hentai movies like sex shows and striptease. Watersports pornography features sexual activities involving urine, such as golden showers. Group sex is sexual behavior involving more than two participants. When sexual activity is centered on one of the threesome, then the activity may be described as a gang bang of the person. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. However, the tradition of bondage magazines continues in the form of art books of bondage photographs, published by mainstream publishers such as Taschen. Especially popular in post-World War 2 Japanese culture. This style of filming is in contrast to having a separate, third-person camera crew filming all the action. A male voyeur is nude milfs commonly labeled Peeping Tom, a term which originates from the Lady Godiva legend. The person sat upon may be in bondage, sexually submissive, or simply held down by the body-weight of the other person. For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. Can also include auto-fellatio, or performing oral sex on oneself. Some do not use the diapers at all, for arousal, or bladder gaysex and bowel movements. The term is a slang word that originated in the gay community and comes from the equestrian term bareback, which refers to the practice of riding a horse without a saddle.