The oldest archaeological chess artifacts, ivory pieces, were excavated in ancient Afrasiab, today's Samarkand, in Uzbekistan, Central Asia, and date to about 760, with some of them possibly older. The oldest known chess manual was in Arabic and dates to 840–850, written by al-Adli ar-Rumi (800–870), a renowned Arab chess player, titled "Kitab ash-shatranj" (Book of the chess). This is a lost manuscript, but referenced in later works. The eastern migration of chess, into China and Southeast Asia, has even less documentation than its migration west. The first reference to Chinese chess, called "xiàngqí" , appears in a book entitled "Xuán guaì lù" ("Record of the Mysterious and Strange"), dating to about 800. Alternatively, some contend that chess arose from Chinese chess or one of its predecessors, although this has been contested.