7Waddell, John. "Rathcroghan - A Royal Site in Connacht." The Journal of Irish Archaeology 1 (1983): 21.
The quotation is from the Tain Bo Fraich: "This was the arrangement of the house: seven partitions in it, seven beds from the fire to the wall in the house all around. There was a fronting of bronze on each bed, carved red yew all covered with fair varied ornament. Three rods of bronze at the step of each bed. Seven rods of copper from the centre of the floor to the ridge-pole of the house. The house was built of pine. A roof of slates was on it outside. There were sixteen windows in it, and a shutter of copper for each of them ..." (Byrne and Dillon 1937, 3)
Waddell's journal article may be read in its entirety here.