Kung Fu Horse Stance: Powerhouse of the Martial Arts

In olden days many masters would have their students perform the simple horse stance for hours on end. The horse stance is found within practically every martial art.Is this simple posture nothing but a strengthening exercise? Or is there more than meets the eye? In this book an addition to his first book Kung Fu Scholar Methods, Sifu Li Jung Yuen goes into more detail on the simple horse stance and it's importance in internal martial arts.