Physicians with Head Mirrors
Ever wonder where the stereotypical headband mirror thing that you see on old illustrations of doctors came from?
It's actually a reflector. Before we had battery-powered and flexible electrical lights, gas and oil-powered flames were the best we could do, but you don't want to put that too close to the patient.
The concave reflective surface of the mirror focuses the diffuse light to a point inside the patient, which the physician can see through the hole in the center of the device.
Today, these reflectors are not frequently used in developed nations, as their primary purpose (otolaryngology - that is, ear, nose, and throat doctors) now has instruments which can illuminate the cavities being examined without an external source of light. However, they're still very useful in countries with intermittent or unreliable power sources, and are often kept on hand in surgical suites and hospitals in those countries, in case of power outage during a procedure.
Diseases of the Nose and Accessory Cavities. W. Spencer Watson, 1890.