Ten Things I Wish I Could Have Understood about Taubman Technique from the Very Beginning
5. How to “trick” your hand so that your thumb can bear the weight of the arm.
As Thomas Mark points out, it is possible to create an arch between the bones of the forearm, the wrist bones, and the bones of the fingers. This arch has great potential for load bearing in much the same way that an architectural arch does. It is biomechanically a great idea to capitalize on that potential if you are a pianist.
However, there is no such natural arch shape between the bones of the thumb and the bones of the wrist and forearm. The thumb simply attaches at the wrist differently, its joints moving on a perpendicular to those of the fingers. For this reason and because the thumb’s ligaments are particularly loose and elastic, it takes sleight of hand (so to speak) to rest the arm on the thumb. But if you are trying to build a coordination where landing on the thumb automatically raises the pinky side of the hand, then you need to be able to do exactly that.
This cannot be emphasized strongly enough. If you don’t 1) create the hand architecture that allows arm weight to rest on the thumb, and 2) use it to that effect--a major percentage of the technique’s biomechanical efficiency will be lost. Besides, the thumb will sound different from the other fingers because it doesn’t have the arm’s weight behind it, and you will therefore stand to lose the benefits of the expressive logic of the technique.
The instruction to stand on the thumb nail begins to address this issue. But I don't think it provides the body with enough information about what sensations to create to make this technique work, and work well. Without insight, you could practice for months without getting the all-important benefits of landing well on the thumb.