This recipe appears in the book 'The edible mollusks of Great Britain and Ireland, with recipes for cooking them' by MJ Lovell, published in 1867. It is a free eBook that is available from Google Books, and freely downloadable from from Google Books if you have a mobile device. This book covers what sort of shelled creatures you can get away with eating in the UK.
The quantities for this bizarre recipe are very much up to you. But I would urge you to have a go, just make sure that you don't strip the landscape of Limpets, as that would be selfish and destructive.
1. Wash them and free the shells from seaweed etc put them into a saucepan and parboil them.
2. Take them out of the shells chop up some parsley and put it with a tablespoonful of oil or an ounce of lard or butter into a saucepan and fry until it becomes brown
3. Add a pint of water and when boiling throw in the limpets with a teaspoonful of anchovy sauce some pepper and boil again for half an hour or if preferred stew them before putting them into the soup.