Have you ever picked up two grapefruits that looked alike, but felt like a different weight in each of your hands?
The next time you are at a supermarket, practice with such fruits and simply determine for yourself which one is heavier; then confirm it on the weight scale.
Using a delicate balancing scale at home, do the same thing with dissimilar, but smaller objects -- matches, pens, pencils, smoking pipes, spoons, etc.
Hold one in each hand and ascertain for yourself the weight differences of each object.
You'll probably find that the larger, and heavier items are easier to decipher, but practice will allow even the subtle weight differences of smaller objects to be determined as well.
Then by feel alone, determine the exact weight of single objects.
You can also fill similar glasses with different amounts of water and discern the heaviest to lightest ones with your eyes closed.
Remember these exercises are designed to make use of the latent areas of your brain.
Whether you find an immediate use for your newly acquired skills or not is irrelevant.
Pathways and avenues in the quagmires of the mind are being opened up.
These in turn will lead to other areas and so forth.
The more mental and physical skills that you acquire, the easier it will be to acquire others.