Einstein, The World's Smallest Miniature Horse

The Falabella miniature horse was originally developed in Argentina in 1868 by Patrick Newell. When Newell died, the herd and breeding methods were passed to Newell's son-in-law, Juan Falabella. Juan added additional bloodlines including the Welsh Pony, Shetland pony, and small Thoroughbreds. With considerable inbreeding he was able to gain consistently small size within the herd.
South Africa's Miniature Horses were developed in that nation and are known as the South African Miniature Horses, a recognized breed in its own right. Mr. Wynand de Wet of Lindley, South Africa, started in 1945 with two Shetland mares and a stallion. Through strict selection, their offspring became smaller and in 1991 Mr. de Wet bred a mare that was only 66 centimetres (26 in) tall.