Stri Parva 15.27

Conversant with the rules of righteousness, the Kuru queen, possessed of great foresight, turned her eyes from within the folds of the cloth that covered them, to the tip of Yudhishthira's toe, as the prince with body bent forwards, was about to fall down at her feet. At this, the king, whose nails had before this been all very beautiful, got a sore nail on his toe.