48Wilde, William Robert. The Beauties of the Boyne, and Its Tributary, the Blackwater. Dublin: James McGlashan, 1850. 193.
Wilde's account of this stone may be read in its entirety here.
Michael Herity observes that the decorated stone that forms the exterior edge of what we now call the "roof-box" was not noted by Petrie, in 1833. Thus Herity suggests "we can limit the date of its discovery to a period of, at most, 15 years (1833-48). It may have been that it was the work of the Ordnance Survey in this area in 1836 that brought [the stone] to light or, alternatively, the work recorded by Lord Albert Conyngham in 1842 which revealed further gold objects." (Herity, Michael. "From Lhuyd to Coffey: New Information from Unpublished Descriptions of the Boyne Valley Tombs." Studia Hibernica 7 (1967): 136.)