आगमे विश्वासटिप्पन्यः

(“five-fires asceticism”) Form of voluntary physical mortification, usually performed in the hot season, in which the
person sits surrounded by four fires, the
fifth fire being the sun overhead.
Although this practice is now uncommon, it is very old and routinely named
in the puranas and other religious texts
as one of the standard ascetic practices.
As with all forms of physical ascetic
endurance (tapas), this rite is performed
under the assumption that voluntarily
enduring pain and/or hardship is a
way to gain spiritual, religious, and
magical power.