There is an "X" carved through the wall, splitting it into four sections. The top, bottom, left, and right sections are, respectively, an egyptian eye, the chinese yin-yang, an hourglass, and a spiral. Now that you've read the riddle, they seem to glow with a mysterious white light. "which one..." says the raspy whisper that greeted you. You decide to examine the picture that represents the answer to the riddle.