The earliest reference to a boundary stone in Greek literature is in the "Iliad", which describes the goddess Athena using one as a projectile. Boundary stones, known as "horos", could be made of either carved or undressed stones, and were typically inscribed with the Greek word "horos". One such stone was used to indicate the edge of the Athenian "agora". The practice of separating areas of land with boundary stones, though common, was widely considered by classical writers to be a violation of the principle of communal land ownership.