Short answers, pulled from the story.
A wax tablet is a wooden board covered with a layer of wax, used as a reusable and portable writing surface. A pointed stylus pressed text into the wax, and the flat opposite end of the stylus smoothed the surface for erasure and reuse. Tablets were used for students' notes, business accounts, and early shorthand.
The oldest surviving wax tablet is a boxwood writing tablet with an ivory hinge recovered from the Uluburun Shipwreck near Kas in modern Turkey in 1986. The wreck dates to the 14th century BC, making the tablet over three thousand years old.
Tabula rasa is a Latin expression meaning a smoothed or blank wax tablet, referring to the act of erasing the wax surface for reuse. The modern English phrase "a clean slate" derives directly from this Latin term.
Wax tablets were used from at least the 14th century BC through to the 19th century AD. The salt mining authority at Schwabisch Hall employed wax records until 1812, and the fish market in Rouen used them until the 1860s.
Medieval wax tablets used a writing surface made from beeswax combined with five to ten percent plant oils and carbon pigments, giving the wax a brownish-black colour. This mixture had a melting point of about 65 degrees Celsius. The boards themselves were made of wood.
A carved stone panel from the South-West Palace of the Assyrian ruler Sennacherib at Nineveh, dated between 640 and 615 BC and held at the British Museum as ME 124955, depicts a figure holding what appears to be an open diptych. A similar figure appears in the Neo-Hittite Stela of Tarhunpiyas, now in the Musee du Louvre under accession number AO 1922, dating to the late 8th century BC.