Abu Abdallah Muhammad ibn Ahmad al-Jayhani

His lost geographical work (which was preserved in later authors' books) is an important source of 9th-century history of Central Asia and Eastern Europe.

Despite being unable to recover the provinces, the Samanids employed numerous local Daylamite and Gilite leaders and remained active in the struggles there.

[7] Ahmad ibn Fadlan, who met him in 921, recorded that the people referred to him as "the elder bulwark", evidencing that Jayhani was still regarded as a most influential figure in Nasr II's court.

[14] Jayhani "assembled around himself some foreigners and questioned them about the countries and their revenues, the condition of roads thither, the elevation of the stars above the horizons there and the length of the meridian shadows cast by the sun", according to al-Muqaddasi.

[2][13] The total book (Arabic: كتاب المسالك والممالك, romanized: Kitāb al-Masālik waʿl-Mamālik) spanned seven volumes and was said to also incorporate the whole of Ibn Khordadbeh's work.

[8][15] His work informed the later Muslim geographer Ibn Hawqal, who used Jayhani's book, and described a mountain stretching "along the spine of the earth".