Cipher books are another example of Domiran practicality utilizing Mian ingenuity. To transmit a message using a cipher, both sender and receiver must have identical texts-usually a copy of some common manuscript. The sender records the position of words in his text, sends those positions to the receiver, who then looks up the words of the message. The concept behind ciphers was discussed by Mian philosophers and occasionally used by Mian rulers, but was truly standardized and perfected by the Domirans. The Arcanii often use cipher books while traveling incognito and in foreign lands, because the presence of such an apparently innocuous piece of writing is not immediately incriminating.