This particular recipe comes from a more recent cookbook, but the original recipe is tracable to 15th century Scotland, I have many variations on this recipe from different sources.
Title: Scotch Barley Broth
Categories: Soups/stews Canadian
Yield: 1 Servings
2 lb Shoulder of mutton
1 c Dried green peas
1/2 c Pearl barley
2 qt Cold water
2 ts Salt
1/4 ts Pepper
2 Onions chopped
3 Carrots diced
1 c Turnip diced
1/2 c Celery diced
1 tb Parsley chopped
Soak green peas overnight and soak barley for 2 hours.Wipe meat and
trim off fat.Put into broth pot with cold water salt and pepper.
Slowly bring to the boiling point and skim.Add peas,barley and
onions and simmer gently for 2 hours.Cool then skim fat from broth.
Bones may be removed if desired.Add carrots,turnip and celery and
simmer 30 minutes until vegetables are tender.Season with more salt
if needed and pepper to taste.Twenty minutes before serving add
parsley and remove any film of fat that has gathered on the surface.
Out of Old Nova Scotia Kitchens by Marie Nightingale
The book mentions Portable Soup (sometimes called Pocket Soup or Glue) that was made by simmering stock for 12 hours and then boiling/stirring constantly for 8. Then solid stock was formed into small cakes. Sea-faring men and woodsmen could carry them in their pockets.