His followers also wore felt and walked barefoot.[6] According to al-Jawbari in his book Kashf al-Asrar (Unveiling the Secrets)"members of the Haydariyya dervish order took Hashish before staging their performances of self-mutilation, in order to numb the pain."[7] Al-Jawbari's Kashf al-Asrar was written in 13th century Iraq.