Short answers, pulled from the story.
The Keśin Hymn appears as hymn 10.136 within the Rigveda, an ancient Indian sacred collection of Vedic Sanskrit hymns. This text dates to the second millennium BCE according to scholarly consensus on the Rigveda's composition period.
Werner 1998 describes these lone ascetics as living a life of renunciation and wandering mendicants without fixed homes. They traveled with the wind while clad only in dust or yellow tatters according to the hymn's description.
Yāska around 500 BCE offered multiple interpretations linking Keśin to either the sun god Surya or orgiastic intoxication practices. Sāyana writing in the 14th century ACE supported the solar interpretation followed by early European Sanskrit scholars including H. H. Wilson and M. Bloomfield.
Flood 1996 notes they experienced heightened altered states of consciousness that allowed them to soar through the air. These practitioners possessed mystical powers enabling movement alongside deities like Vayu and Rudra.
Karel Werner identifies this concise hymn as the earliest evidence of yogis and their spiritual tradition existing before later developments. The text depicts long-haired ascetics experiencing altered consciousness states that prefigure classical yoga methods.