Trilingual cuneiform inscription of Xerxes at Van Fortress in Turkey, written in Old Persian, Akkadian, and Elamite

It is a letter, and the script is cuneiform, the date ~2400 BC

Cuneiform script is one of the earliest known systems of writing. It used wedge-shaped marks on clay tablets, made by a reed stylus. The name cuneiform itself means "wedge shaped", from the Latin cuneus "wedge" and forma "shape". It came into English usage probably from the Old French cunéiforme.