The automatic maid of Philo of Byzantium (3rd century BC), is the first functioning robot in history.

It is a humanoid robot in the form of a maid (life-size) holding a jug of wine in her right hand.

When the visitor placed a crater (cup) in the palm of her left hand, she automatically poured firstly wine and then water into the crater according to his desire to mix.

According to Philo the Byzantine, in the chest of the maid were two watertight containers filled with wine and water respectively. At the bottom of these were two tubes which led their contents through her right hand to the edge of the jug of wine. Two air ducts emanated from the top of the containers penetrated their bottoms and ended in her belly.

Her left arm was hinged to her shoulders, while a spiral rod (spring), eccentrically placed in its extension, held it up. From the same point(key) two tubes descended, entering and blocking the curved, perforated ends of the air ducts. The key pipes had two holes at their ends, the hole that communicated with the wine container preceding the one that communicated with the water. When the crater was placed in the palm of the maid's hand, her left hand went down and the key tubes were lifted. The hole of one tube was aligned with the air tube of the wine jar, air entered the jar, and wine flowed from the wine jar tube into the crater. When the glass was half full of wine, the hand continued to go down due to the weight, the passage of the wine's air tube was blocked and the flow stopped.

At the same time, the hole of the second tube was aligned with the air channel of the container with the water and water began to flow to dilute the wine. When the cup was filled, the hand continued to go down (due to the weight), the passage of the air channel of the water was blocked and the flow stopped. Also, when the crater was removed at any time, the left hand was raised, the key tubes were lowered, the blockage of the air channels, the creation of a vacuum in the containers and the flow of liquids stopped.

The maid, therefore, filled the visitor's cup with pure wine or diluted with water, in the quantity he desired, depending on when he would draw it from her palm.