Per the Neue Deutsche Biographie entry (Rudolf Wilhelm, 1982), Lahmann developed and sold the “Dr. Lahmann-Unterkleidung,” a purely cotton, large-mesh reform underwear, and set out his clothing-reform argument in his book “Die Reform der Kleidung” (1898, 4th ed. 1903). The claim is classified as testimonial (resting on Lahmann’s own clinical and theoretical say-so, not a measured comparison) and unreplicated: none of the cited sources documents a controlled comparison of the reform garment against ordinary clothing on any circulatory or health outcome.