Al-Hasan al-Yusi (b. 1040/1631, a village in the upper Moulouya valley of the Middle Atlas – d. 15 Dhu'l-Hijja 1102/9 September 1691) belonged to the Ayt Yusi branch of the Sanhaja Berbers; the nisba "Yusi" derives from his ancestor Yusuf. TDV regards him as the greatest Moroccan scholar of the 17th century, an authority in Sufism, poetry, linguistics, logic, kalam and law. His Sufi affiliation was the Shadhiliyya (first the Nasiriyya branch of Ibn Nasir al-Dar'i, later Jazuli influence); he is famed for his letter "Bara'at al-Yusi" admonishing Sultan Mawlay Isma'il. He died returning from pilgrimage in 1102/1691, and a mosque and tomb were built in his name near Sefrou, south of Fez. As no two independent numeric coordinate sources exist for the tomb, the coordinate is left null (descriptive location: near Sefrou; settlement village Tamazzarite). There is no dispute over the burial. (Source: TDV Encyclopedia of Islam "Yûsî"; en.wikipedia "Al-Hasan al-Yusi".)