First century inventor Hero of Alexandria is known for a practical description of which invention?

Hero published a practical description of a steam-powered device called an aeolipile (sometimes called a "Hero engine"). Water is heated in a cauldron, producing steam under pressure. The steam exits the turbine (a ball atop the cauldron) which rotates on an axis, creating torque. The aeolipile Hero described is considered to be the first recorded steam engine or reaction steam turbine.

Hero of Alexandria, also known as Heron of Alexandria was a mathematician and engineer who lived in Alexandria, Roman Egypt during the 1st century A.D. He is considered the greatest experimenter of antiquity and his work is representative of the Hellenistic scientific tradition.

Among his most famous inventions was a windwheel, constituting the earliest instance of wind harnessing on land. He also is credited for inventing an early vending machine. It was a dispenser of holy water in temples. A coin was dropped into an opening that would cause a valve to open and allow water to flow, a counter weight would stop the flow after the coin fell off the collection pan. Much of Hero's original writings and designs have been lost, but some of his works were preserved in Arabic manuscripts.