A recent work proposed that the double spiral motif found at Newgrange (ca. 3200 BC) is a calendrical representation. Looking south the northern peoples observed that the arc traced by the sun widens steadily from winter solstice to midsummer. A natural supposition is that what is actually observed is just a part of a spiral, its lower half being hidden below the horizon. This seems to be strikingly original in contrast with our habit to think about circles. The author mentions just two refs from the 1980's (M.Brennan 1983, N.L. Thomas, 1988), where this interpretation has been made. Besides vague generalisations, such as "solar motif", are there earlier mentions of the idea as explained along the lines given here?