"Concentration, of course, comes from various sources. Through the senses you can get concentration. Some get it when they hear beautiful music, others when they see beautiful scenery. ... Some get concentrated by lying upon beds of spikes, sharp iron spikes, others by sitting upon sharp pebbles. These are extraordinary cases [using] most unscientific procedure. Scientific procedure is gradually training the mind... The value of ethics to the Yogi lies in that it makes the mind pure. The purer the mind, the easier it is to control it. The mind takes every thought that rises and works it out. The grosser the mind, the more difficult [it is] to control [it]."

- Swami Vivekananda, "Concentration" (March 16, 1900, Washington Hall, San Francisco)[recorded by Ida Ansell], Lectures and Discourses, Complete Works: Vol 4