Alt method: http://www.foodnetwork.com/recipes/alton-brown/barley-water-recipe/index.html
Just made a batch. Used non-pearled barley. Fabulous -- and you can cut the honey down or even out. Save the barley and put it in soup or have it with good cinnamon, etc.
Also the reliable Mrs Beeton version (link):
Mode.--Wash the barley in cold water; put it into a saucepan with the above proportion of cold water, and when it has boiled for about 1/4 hour, strain off the water, and add the 2 quarts of fresh boiling water. Boil it until the liquid is reduced one half; strain it, and it will be ready for use. It may be flavoured with lemon-peel, after being sweetened, or a small piece may be simmered with the barley. When the invalid may take it, a little lemon-juice gives this pleasant drink in illness a very nice flavour.
Time.--To boil until the liquid is reduced one half.
Sufficient to make 1 quart of barley-water.