Was Abd al-Rahman ibn Muljam mutilated after he killed Imam Ali?

Some narrations, whose authenticity we cannot ascertain, state that the guardians of Imam Ali's blood—may Allah be pleased with him—mutilated Ibn Muljam's body after his killing, and there was disagreement as to who did this. Dr. Ali Muhammad Al-Sallabi denied the authenticity of this in his book on the biography of Imam Al-Hasan ibn Ali—may Allah be pleased with them both—emphasizing that what is correct and befitting of Al-Hasan, Al-Husayn, and the children of the Prophet's household is that they adhered to the وصية (bequest/will) of Amir al-Mu'minin Ali regarding the treatment of Abd al-Rahman ibn Muljam. This demonstrates the great ethics of Islam in forbidding mutilation and adhering to lawful retribution (Qisas).