
The Ballard rug, named for the American collector James Ballard, is probably the best known prayer rug in the world. This Ottoman court carpet was woven in the late 16th century. (ca. 1580)
This rug is owned by the Metropolitan Museum of Art (not currently on display)
http://www.metmuseum.org/Works_of_Art/collection_database/islamic_art/carpet_with_triple_arch_design//objectview.aspx?OID=140004751&collID=14&dd1=14