Quotation from: The Gods of Mars

Written by: Edgar Rice Burroughs

Then he commenced groping his way about the floor of the dark
chamber searching for the trap that led to the corridors beneath.
At length he summoned me by a low, "S-s-t," and I crept toward the
sound of his voice to find him kneeling on the brink of an opening
in the floor.

"There is a drop here of about ten feet," he whispered. "Hang
by your hands and you will alight safely on a level floor of soft
sand."