The Kelloggs pioneered the process of making flaked cereal. Because of the commercial potential of the discovery, Will wanted it kept a secret. However, John allowed anyone in the sanitarium to observe the flaking process and one sanitarium guest, C. W. Post, copied the process to start his own company. That company became Post Cereals and later General Foods, the source of Post's first million dollars. This upset Will to the extent that he left the sanitarium to create his own company.