Approaching 60, Isabella Bird rode on horseback alongside a British military unit across dangerous terrain, armed with a revolver and a medicine chest. Yet for much of her early life the same woman was bedridden with a spinal condition, chronic insomnia, and crushing headaches. This deep dive explores the mechanics of that astonishing transformation.

Handed 100 pounds and told not to come home until it ran out, Bird turned a doctor's prescription for fresh air into a legendary career as a global explorer, best-selling writer, and medical pioneer. She carefully curated a respectable public image while riding astride through the Rockies and later forced the world's most exclusive scientific institutions to admit their first woman.

• Her first book, "An Englishwoman in America," built from letters home
• Climbing Hawaiian volcan ...