Upanishad and Ashtanga yoga

The essence of the Upanishads are about the relationship of our being with the Being of the Universe. That realization is achieved through meditation (yoga) to become merged in Brahma. The end in view in the classical Ashtanga Yoga is also the same. Then where is the difference?

The elements of yoga thought found in various Upanishads of course must have given rise to the ideas of Sankhya and Yoga, the two most important of the six Indian Darsanas or philosophies. The basic text of the classical yoga is the Yogasutra of Patanjali, the great Indian sage. In the sutras (aphorisms), Patanjali explains specific and scientific methods for self-realization. The Upanishads on the other hand expound no such method.