Sylvester Stallone introduced British supermodel Kate Moss to rumpology, the art of predicting a person’s future by looking at their posterior, as the celebs vacationed in Ibiza over the weekend.

“I’ve never seen anybody get so animated over butts and Elvis as those two,” an onlooker revealed to Britain’s Star Magazine, adding that Sly allowed Kate to practice rumpology by peeking at his wife Jennifer Flavin’s rear.

The supermodel has been left fascinated by the odd ritual.

“She can’t wait to get back home and read her boyfriend Jamie Hince’s cheeks. Although she doesn’t know how to broach the subject!”