Jerome K Jerome's 'Three Men in a Boat' of 1888 has, "For the next four days he lived a simple and blameless life on thin captain's biscuits (I mean that the biscuits were thin, not the captain) and soda-water."
Original Receipt from 'Modern Cookery for Private Families' by Eliza Acton (Acton 1845);GOOD Captain's BISCUITS.
Make some fine white flour into a very smooth paste with new milk; divide it into small balls; roll them out, and afterwards pull them with the fingers as thin as possible; prick them all over, and bake them in a somewhat brisk oven from ten to twelve minutes. These are excellent and very wholesome biscuits.