Hiking equipment
According to Tom Brown, the basic plan for survival is in the order of shelter (including clothing), water, fire, and food. Cody Lundin writes about the "Rule of 3s"; this relates to human survival without basics: three minutes without air, three hours without shelter, three days without water, or three weeks without food.
Prahlad Jani
Two observational studies of Jani have been conducted, one in 2003 and one in 2010, both involving Dr Sudhir Shah, a neurologist at the Sterling Hospitals in Ahmedabad, India, who had studied people claiming to have exceptional abilities, including other fasters such as Hira Ratan Manek. In both cases the investigators confirmed Jani's ability to survive healthily without food and water during the testing periods, although neither study was submitted to a scientific journal. When questioned six days into the 2010 experiment, the DRDO spokesperson announced that the study's findings would be "confidential" until results were established, and a further official press release by the team stated that any inside analysis information may be disclosed only at the discretion of the principal investigator, DIPAS. Uninvolved doctors and other critics have questioned the validity of the studies and stated their belief that, although people can survive for days without food or water, it is not possible to survive for years, especially since glucose, a substrate critical to brain function, isn't provided. The veracity of Mataji's claims has also never been independently confirmed with all tests being indigenously conducted.