There is a pearl with nine bends (there is an aperture inside, and the aperture is bent nine times), which needs cotton thread to pass through. Nobody can. Someone thought of a way to tie the cotton thread to the ant, and then paint a pearl hole with balsam, so that the ant can enter from the other end of the hole and climb to the opposite side.
Legend has it that this story seems to come from Princess Wencheng who proposed to the Tang King by Songzan Gambu. The king of Tang set this question to test him, and it was solved.