In Caverns Below by Stanton A. Coblentz — Read

Realizing that I was attempting an experiment which might lead to disaster, I took one or two simple precautions before visiting Thuno Flâtum. The first was to disguise myself, for I did not want it known that it was a stranger, a foreigner, a "colored barbarian," who was challenging the throne of the Dictator. The disguise was accomplished simply enough, largely by means of some chalk-like powder, with which I made my face milky pale; in addition, I used a pair of heavy amber glasses, so as to conceal the gray of my eyes; and I steeped my hair in an ashen dye, in order to give it the complexion considered normal. Thus equipped, I was hardly to be distinguished from the average man of Wu.

But as I drew near the Dictator's headquarters, it occurred to me to take another precaution. Was I not in danger from fanatics who, furious at my interference with the air-supply, might waylay me and seek my life? With this thought in mind, I dropped back to a position toward the rear of the procession, after giving instructions as to where my henchmen were to proceed. And well that I did so! When we had come to within half a mile of that brilliant cavern where Thuno Flâtum held court, we were impeded by a rabble, partly curious, partly hostile, who flung stones and epithets, and distributed some "sneeze-gas bombs," by which half a score of my followers were disabled.