Hidden away in the Freer-Sackler Gallery website is the following jewel, combining photography, historical watercolor paintings, and archival research:
Yogic Identities: Tradition and Transformation by James Mallinson:
The earliest textual descriptions of yogic techniques date to the last few centuries BCE and show their practitioners to have been ascetics who had turned their backs on ordinary society. These renouncers have been considered practitioners of yoga par excellence throughout Indian history. While ascetics, including some seated in meditative yoga postures, have been represented in Indian statuary since that early period, the first detailed depictions of Indian ascetics are not found until circa 1560 in paintings produced under the patronage of Mughal Emperor Akbar (reigned 1556–1605) and his successors. These wonderfully naturalistic and precise images illuminate not only Mughal manuscripts and albums but also our understanding of the history of yogis and their sects. Scholars have argued for these paintings’ value as historical documents; their usefulness in establishing the history of Indian ascetic orders bears this out. The consistency of their depictions and the astonishing detail they reveal allow us to flesh out—and, sometimes, rewrite—the incomplete and partisan history that can be surmised from Sanskrit and vernacular texts, travelers’ reports, hagiography, and ethnography.
I have eliminated a bunch of footnotes from the quoted text, but you can find them in the original. Mallinson’s photos of yoga ascetics of today’s India and watercolor paintings from the Mughal era create a visual dimension rarely found in academic research.