Clay tablet
Small tablets made out of clay were used from late 4th millennium BC onwards as a writing medium in Sumerian, Mesopotamian, Hittite, and Minoan/Mycenaean civilizations. Sumerian cuneiform characters were engraved on the tables using a stylus. Later the tablets were left to dry or even fired in a kiln.
Collections of these clay documents made up the very first archives. They were also at the root of first libraries.
In the Minoan/Mycenean cultures writing has not been observed for any use other than accounting. Tablets serving as labels, with the impression of the side of a wicker basket on the back, and tablets showing yearly summaries, suggest a sophisticated accounting system. In this cultural region the tablets were never fired deliberately, as the clay was recycled on an annual basis. However, some of the tablets were "fired" as a result of uncontrolled fires in the buildings where they were stored. The rest are still tablets of unfired clay, and extremely fragile; modern scholars are investigating the possibility of firing them now, as an aid to preservation.