A common scene on Mesopotamian terracotta plaques features a couple having sex on a bed, viewed from above (BM 115719).
A set of 7th century Akkadian incantations were designed to produce “ŠÀ.ZI.GA” (“rising of the heart”), a term for successful male sexual performance, which I translate below as “erection.” In other words, they were the ancient Mesopotamian equivalent of Viagra.
This is one of the most concise and well-preserved examples. I have included the accompanying ritual and the Akkadian transcription of the spell, in case anyone wants to try this at home (Results Not Guaranteed). This particular ritual is one of the simpler ŠÀ.ZI.GA ones; others include tying a live ram to the man’s bed or rubbing his genitalia with a mixture of oil and iron ore.
May the wind rush and the garden tremble! 
May the cloud thicken and the shower fall!
May my erection be rushing river water.
May my penis be a harp string, 
so it cannot slip out of her. 
Take a harp string. Tie three knots in it. Recite the incantation seven times. Tie it around his right and left hands.
Via Archaeology Blog dedicated to the greatest ancient culture – Mesopotamia.