 The 19th century "Sritattvanidhi" describes and illustrates the pose.The name, and the more general name Yogasana which may denote a variety of similar poses, is found in much older documents as a meditation seat, such as in the 4th century "Darshana Upanishad".While opening the hips and lengthening the spine, the asana's relative ease on the knees makes it easier than siddhasana or padmasana for people with physical difficulties.