حجر الفلاسفة
He then worked with minerals and natural salts using distillation and crystallization methods borrowed from Jabir ibn Hayyan and Muhammad ibn Zakariya al-Razi. When these failed he turned to vegetable and animal material, finally using human blood and urine. He gradually sold his wealth to buy secrets and hints towards the stone, most often from swindlers. He traveled all over the known world, including the Baltics, Germany, Spain, France, Vienna, Egypt, Palestine, Persia, Greece, Turkey, and Cyprus, to find hints left by past alchemists. His health had been deteriorating, most likely from the fumes he had created with his alchemy. He retired to the Island of Rhodes, still working on the Philosopher's stone until his death in 1490.