Dr. Mikao Usui was a teacher of Christianity at a university in Kyoto in the mid 1800s. His students had questions surrounding Jesus' healing powers and asked Dr. Usui for his thoughts. Being a Christian, Dr. Usui did believe that Jesus had healing powers and he was then asked by his students to perform one to prove Jesus' healing powers so that they could believe as well. He didn't know how to heal and so began his journey to figure it out. Dr. Usui talked to church leaders, went back to school and eventually he climbed Mt. Kurama for a 21 day meditation and fasting ritual to figure things out.
At the end of his 21 day retreat Usui was about to leave and he saw a great light approaching him from the distance. Of course, as anyone would be, he was fearful, but he stayed. The light came at him, struck him in the forehead and knocked him unconscious. Upon waking, it is said that he saw millions of small glowing bubbles and the Reiki symbols were shown individually to him as well as the meaning and application of the Reiki symbols.
On his journey down the mountain, Dr. Usui fell and hit his toe (healed it with Reiki) and continued his healing practice until he returned to Kyoto. He found that those who he had practiced Reiki on would return for treatments because they were so beneficial. He passed on this healing system to Mr. Chujiro Hayashi and then he taught it to Mrs. Takata, and the teaching chain continues. Over the years, many masters have added or taken away some techniques and modified the teachings and that's great for them. I practice the classical way, plain and simply and I feel this method is very beneficial.