Bhagat Beni Ji has three hymns in the Guru Granth Sahib Ji, in Sri, Ramkali and Prabhati. Nothing about him is established. No region, no century, no caste, no lineage.
The Ramkali composition is a detailed account of yogic physiology, the channels, the chakras, the reversed flow, written by someone who plainly knew the system from the inside. The Prabhati composition is an attack on outward piety in a man whose private conduct is rotten.
He is the clearest case in the volume of a text preserved with the author lost. The editorial principle in 1604 was evidently the composition and not the credentials.
Every biography of him in circulation is inference from the three hymns.
The Sri Raag hymn and the Ramkali composition are very different in method. One is a warning against a life spent on appearance, addressed to a listener who thinks himself secure. The other is technical, using the vocabulary of the hatha yoga tradition, the ida and the pingala and the sushumna, the moon and the sun, the tenth gate.
The Ramkali composition is one of the places in the Guru Granth Sahib Ji where yogic terms are used at length rather than argued against. The reading generally offered is that the terms are taken over and given a different object, the practice redirected from the body to the Name.
No shrine anywhere is associated with him and no community claims descent from him. He is three texts and a name, which is what the volume preserves of several of its contributors.