A black buoy with a beacon pole ontop is shown marking the western end of the causeway on an historic chart. Admiralty Sailing Directions dating to 1870 note 'A conical buoy with staff and diamond, marked 'Causeway' with black and white rings, has been placed near the west end of the Sarn Badrig in 5 fathoms at low water springs'.
Sources include:
Admiralty, 1870, Sailing Directions for the West Coast of England from Milford Haven to the Mull of Galloway including the Isle of Man, pg53
Historic Admiralty Chart 1484_A1B, RCAHMW digital collections sourced from the UK Hydrographic Office and first published in 1843
