In Farid al-Din Attar's Asrar Nameh, the tale of Nizam al-Mulk and the Sufi's leather flask (rekveh) serves as an allegory for the insatiable nature of worldly desire and the superior spiritual detachment of Sufis. An old Sufi challenges the grand vizier Nizam al-Mulk to fill his small leather flask with gold. Underestimating the request, Nizam attempts to fill it, but the flask behaves like a bottomless pit, swallowing vast amounts of gold without filling. Once it is finally filled, the Sufi dramatically pours the gold over Nizam's head and throws the empty flask down. This act illustrates that worldly wealth and power are ultimately meaningless and empty to a true spiritual seeker, while exposing the limits and vanity of worldly rulers who believe their wealth can satisfy spiritual poverty.