Traditional Japanese erotic paintings usually show genitals as exaggeratedly large. The oldest known painting of this type, found in the Hōryū-ji Temple in Ikaruga, dates to the eighth century AD and depicts a fairly large penis.The ancient Indian sexual treatise Kama Sutra, originally written in Sanskrit, probably between the second and fourth centuries AD, divides men into three classes based on penis size: "hare" size (about 5–7 cm, or 2–3 inches, when erect), "bull" size (10–15 cm, or 4–6 inches), and "horse" size (18–20 cm, or 7–8 inches). The treatise also divides womens vaginas into three sizes ("deer", "mare", and "elephant") and advises that a man match the size of the vagina of the woman he is having sex with to the size of his own penis. It also gives medically dubious advice on how to enlarge ones penis using wasp stings. Postclassical
In medieval Arabic literature, a longer penis was preferred, as described in an Arabian Nights tale called "Ali with the Large Member". As a witty satire of this fantasy, the 9th-century Afro-Arab author Al-Jahiz wrote: "If the length of the penis were a sign of honor, then the mule would belong to the Quraysh" (the tribe to which Muhammad belonged and from which he descended).The medieval Norsemen considered the size of a mans penis as the measure of his manliness, and a thirteenth-century Norse magic talisman from Bergen, a wooden stave inscribed with writing in runic script, promises its wearer: "You will fuck Rannveig the Red.
A 2020 review in the Journal of Sex & Marital Therapy found that the majority of men believed that the average erect penis length is more than 15.24 cm (6 inches). This inaccurate belief has likely been fed by inaccurate and exaggerated data presented in studies where the size of the participants erect  penis is self-reported. Participants may report overestimates of the size of their penis in the belief that a larger penis is more socially desirable. The same review analyzed the results from ten prior studies where measurements of erect penis size were made by researchers. They reported an erect penis to be between 12.95 and 13.92 cm (5.1 and 5.5 inches, respectively) in length, a result significantly below the average obtained in self-reported studies. The authors commented that results of such measurement studies may still be inflated due to volunteer bias – the possibility that men with larger penises may be more likely to choose to participate in such studies. Erect circumference
Similar results exist regarding studies of the circumference of the adult fully erect penis, with the measurement usually taken mid-shaft. As with length, studies that relied on self-measurement consistently reported a significantly higher average than those with staff measuring. In a study of penis size where measurements were taken in a laboratory setting, the average penis circumference when erect was 11.66 cm (4.59 inches).