In the Graeco-Roman era, a sex manual was written by Philaenis of Samos , possibly a hetaira courtesan of the Hellenistic period 3rd—1st century BC. Most sex acts are typically performed on a bed or other simple platform. Other physical limitations of one or both participants also limit the sex positions which they may adopt. It may be penetrative or non-penetrative, and may take place before, during, as, or following intercourse. There are numerous sex positions that participants may adopt in any of these types of sexual intercourse or acts; some authors have argued that the number of sex positions is essentially limitless. Perhaps the bonobo's most typical sexual pattern, undocumented in any other primate, is genito-genital rubbing or GG rubbing between adult females. Non-penetrative sex or frottage is generally sexual activity that excludes penetration, and often includes rubbing one's genitals on one's sexual partner. Most of these positions can be used for either vaginal or anal penetration.