That is precisely how this feature was recorded, and it survives in the historical record by the slimmest of chances, captured in a single survey before the water that had concealed it crept back, or before the ground was altered beyond recognition.

The story begins in 1952, when drainage works on the Boyle River lowered the water level of the Lough Gara lakes and exposed a remarkable concentration of crannogs, the artificial or partly artificial island settlements used in Ireland from the Bronze Age through to the early modern period. That autumn, Dr J. Raftery and Miss E. Prendergast of the National Museum of Ireland recorded around 150 such features in the lakes and along the river, and a preliminary numbered map was published in 1953 by the project engineer, Mr R. E. Cross. A further reduction in water level that same year revealed additional features, including numerous cairns on both sides of the river below the outlet from Upper Lough Gara. Raftery, already occupied excavating crannogs at nearby Rathtinaun and Tivannagh, found time in addition to supervise an instrument survey of these newly exposed features. The resulting document is known as the Forsyth survey, named after one of the surveyors whose name appears on the finished maps, and it is now held in the National Museum of Ireland. The features recorded in it were not expected to survive, and were not fully understood at the time. No artefacts were recovered from this phase of survey. This particular cairn appears nowhere except in that document, situated on the north bank of the river, roughly ten metres from the stream and ten metres from what was then the old shoreline, a small and precisely measured mark on a landscape that drainage had briefly and unexpectedly made legible.