Attunements are one of the five elements of the system of Reiki. There are many different attunement methods as teachers have added to, or taken away from, traditional processes.
The origin of the attunement is the Japanese reiju which does not include mantras and/or symbols. There are no limits to the number of reiju one can receive. It is believed that Chûjirô Hayashi may have created the basic attunement process that is taught today by adding symbols and mantras to the reiju.
The attunement is sometimes known as an initiation, empowerment, or transformation.