No effort seemed to have been made to trim the walls, and the floor, too, had been left as nature made it, shaped something like a hollow dish by the pressure of expanding gases millions of years ago when the rock was molten.
The very center of the vast floor was the lowest point of all, and some work had been done there, for it was shaped into a rectangular trough thirty feet long by ten wide.

That trough--there was no guessing how deep it might be--was filled almost to the brim with white-hot charcoal, so that obviously there was a means of forcing a draft into it from underneath.
"Now," said the Mahatma, turning to King as usual and ignoring me, "your friend may submit to the test if he wishes.

He may walk on that furnace.
He shall walk unscathed.

I promise it." King turned to me.
"What d'you say ?" he asked.

"I've seen this done before.[2] It can be done.