Scales has been around for a long time. A depiction of an early balance scale in the Papyrus of Hunefer (dated to the 19th dynasty, ca. 1285 BC). Unknown though what units the Egyptians used. The scene shows Anubis weighing the heart of Hunefer.

Veritasium tries to determine why it seems that we are heaviest at night before going to bed and the lightest in the morning.