On the world where the Sangreal had been hidden, Morgan Le Fay had put in place several safeguards to ensure that the key to Merlin's weapon could only be claimed by the most virtuous and true of spirit.
One of Morgan's tests was a time distortion maze. An area of the forest showed anomalous readings of temporal fluctuations, and time within the field had become extremely decelerated. No boundary or warning marked the temporal field, and people or animals who had inadvertently entered the field seemed to be standing still to those outside, but they were in fact moving imperceptibly slowly. Several years of real time might pass in the one or two seconds required to take a single step. A circuitous path of real time wound through the temporal field like a maze.
Carter used the UTD device to determine the fluctuations in the readings in order to pass through the maze without becoming entrapped, however, once the team had entered the field, the temporal distortions affected the UTD readings and the device no longer functioned. Finding a resourceful and deceptively simple alternative, Carter tossed stones ahead of them on the path. The stone moving through space or becoming frozen in time provided a visual reference for the direction of the path in real time. By successfully navigating the temporal field, SG-1 proved themselves worthy and demonstrated prudence over recklessness as described in the Parchment of Virtues.
Cross Reference: Morgan Le Fay, Parchment of Virtues, Sangreal, Sangreal Planet
Episode Reference: The Quest