al-Fadl bin Dakayn, Abu Na'eem الفضل بن دكين أبو نعيم الملائي · The Book of Purification

"The Prophet (ﷺ) wanted to defecate, and he told me to bring him three stones. I found two stones and looked for a third, but I could not find any, so I picked up a piece of dung and brought them to the Prophet (ﷺ). He took the two stones and three away the dung and said: "This is Riks." Abu 'Abdur-Rahman (An-Nasai') said: Riks is the food of the jinn.