Science and technology of the Tang dynasty
The inventor Ding Huan (fl. 180 AD) of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered. In 747, Emperor Xuanzong had a "Cool Hall" built in the imperial palace, which the "Tang Yulin" (唐語林) describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty, written sources mentioned the air conditioning rotary fan as even more widely used.
Air caster
The air caster (originally called the air bearing) was invented by Harry A Mackie in December 1961 as the “pendant air bearing load supporting device” for General Motors Corporation as an alternative to the overhead crane, which ran opposed to a rail, creating friction free movement. In November 1963, Mackie, on behalf of General Motors Corporation, filed a patent for an “air bearing support with automatic air flow regulation”. This was the first air caster designed to be used on the ground.