If I remember correctly, Shivananda was a trained medical doctor. His Yoga teachings were
very physically based, none of this, "forget the body and
just have positive thinking" business.
Part of positive thinking is ”positive” actions, attention to health, strength and flexibility - hence the traditional Yoga asanas, elaborations on Patanjali’s Yoga sutras and teaching of Kundalini Yoga.
He would be the last person to suggest positive attitude of mind is enough.
No one is saying positive attitude of mind is of
no use. At the very least, it won't hurt the situation, and
may even do good.
What is more important however, is correct diagnosis and prescription - as your example of misdiagnosed tuberculosis indicates, surely more important than the attitude with which the diagnosis it is done. A happy misdiagnosis would not do anyone any good.
KUNDALINI Yoga by SRI SWAMI SIVANANDA (has some great photos)
and
Raja Yoga: theory and practice by Swami Sivananda (book on Raj Yoga).