Although the Fogg doesn't date the work, the very unusual nature of the painting with the heavy halo effect may put in line with some of the drawings he did for Alma Strettell's book Spanish and Italian Folk Songs
John Singer Sargent, His Own Work (New York, NY, 1980), in checklist, unpaginated
Alison Weber, "The Fortunes of Ecstasy: Teresa of çvila and the Discalced Carmelite Reform", Harvard Divinity Bulletin, vol. 28, no. 4, pp. 11-15, repr. on cover, repr. p. 11, repr. pp. 12, 15 (details)
Sargent in the Studio: Drawings, Sketchbooks, and Oil Sketches, Harvard University Art Museums, Cambridge, 06/10/1999 - 09/05/1999
Sargent, Emily, and Mrs. Francis
Ormond (Owner). From their brother, the artist, at his death 1925, Gift
of Mrs. Ormond to the Fogg Art Museum 1937.