Amongst the innumerable kingdoms which supplanted the decaying Caliphate only a few of the most important can be singled out for special notice on account of their literary or religious interest.[498] To begin with Persia: in Khurásán, which was then held by the Ṭáhirids, fell into the hands of Ya‘qúb b. Layth the Coppersmith (_al-Ṣaffár_), founder of the Ṣaffárids, who for thirty years stretched their sway over a great part of Persia, until they were dispossessed by the Sámánids. The latter dynasty had the seat of its power in Transoxania, but during the first half of the tenth century practically the whole of Persia submitted to the authority of Ismá‘íl and his famous successors, Naṣr II and Núḥ I. Not only did these princes warmly encourage and foster the development, which had already begun, of a national literature in the Persian language--it is enough to recall here the names of Rúdagí, the blind minstrel and poet; Daqíqí, whose fragment of a Persian Epic was afterwards incorporated by Firdawsí in his _Sháhnáma_; and Bal‘amí, the Vizier of Manṣúr I, who composed an abridgment of Ṭabarí's great history, which is one of the oldest prose works in Persian that have come down to us--but they extended the same favour to poets and men of learning who (though, for the most part, of Persian extraction) preferred to use the Arabic language. Thus the celebrated Rhazes (Abú Bakr al-Rází) dedicated to the Sámánid prince Abú Ṣáliḥ Manṣúr b. Isháq a treatise on medicine, which he entitled _al-Kitáb al-Manṣúrí_ (the Book of Manṣúr) in honour of his patron. The great physician and philosopher, Abú ‘Alí b. Síná (Avicenna) relates that, having been summoned to Bukhárá by King Núḥ, the second of that name (976-997 A.D.), he obtained permission to visit the royal library. "I found there," he says, "many rooms filled with books which were arranged in cases row upon row. One room was allotted to works on Arabic philology and poetry; another to jurisprudence, and so forth, the books on each particular science having a room to themselves. I inspected the catalogue of ancient Greek authors and looked for the books which I required: I saw in this collection books of which few people have heard even the names, and which I myself have never seen either before or since."[499] [Sidenote: The Buwayhids (932-1055 A.D.).]