An 11th-century Description
These snippets are from Ibn Miskawayh, who wrote a history of the Buyids (though organized by caliphal reign) in Arabic in the 11th century.
Account of the proceedings at the reception of [the Buyid emir] Sharaf al-Dawla by the caliph [al-Ta’i’, in 377]
Sharaf al-Dawla embarked in his barge after arches had been erected in his honor on the bank of the Tigris, and the houses on both banks had been decorated elaborately. The caliph held a public reception, at which he bestowed upon him Sultanic robes, with a crown, bracelets and a collar; with his own hand the caliph tied for him two banners, one black and one white; and his deed of appointment was read out in his presence. After leaving the caliph’s presence, he went to see his sister who was married to the caliph, and stayed with her till the afternoon, when he returned to his own palace; the people had been expecting him all the time. When the banner was lifted, it tore and a piece blew away. He regarded this as a bad omen, but the caliph told him that, as the wind had carried away a portion of it, what was presaged was that he should reign wherever the wind blew.
Source, p. 146.
Source, p. 213-5.