From , at the age of 47 in 1906, Workman climbed up to Pinnacle Peak () (which she believed to be ), a subsidiary peak in the Nun Kun massif of the western Himalaya. It was her greatest mountaineering achievement. As Isserman, Weaver and Molenaar point out, the fact that she climbed the mountain at all, without benefit of modern equipment and encumbered by her voluminous skirts, speaks to both her ability and resolve. She set an altitude record for women that would stand until Hetti Dhyrenfurth's 1934 ascent of Sia Kangri C (). Believing that they had both climbed above the 23,000-foot (7,000 m) mark, Fanny and William now considered themselves the leading experts on climbing at altitude.