Farid al-Din Attar kept a pharmacy in Nishapur, which is where his name comes from, and wrote some of the most widely read poetry in Persian. His Conference of the Birds sets the birds of the world debating whether to seek out the Simurgh, the king they have never seen. Each offers an excuse for staying home, the hoopoe answers each in turn with a story, and those who set out cross seven valleys, of seeking, love, knowledge, detachment, unity, bewilderment and finally poverty and annihilation. Thirty birds arrive. What they find is that the Persian for thirty birds is si murgh, and the thing they were looking for is what they have become.
The pun carries the doctrine, and it is a better summary of the annihilation of the self in God than any prose exposition of the period.
Attar's other great work is not poetry. His memorial of the saints is a collection of lives and sayings of the earlier Sufis, and for a number of them, including Rabia of Basra and the executed mystic Hallaj, it is the principal source anyone has. That makes him both an author and, for the historian, a problem, since his purpose was edification rather than record and the material had been circulating orally for centuries. Rumi, who was a child when Attar was old, is said to have met him, and treated him afterwards as a master.