[http://www.nga.gov/content/ngaweb/research/casva/research-projects.html A Project of the National Gallery of Art, Center for Advanced Study in the Visual Arts ]
- Morris, Robert, 15 June 1784, in a letter to George Washington, describing The Hills (later Lemon Hill), estate of Robert Morris, Philadelphia, Pa. (quoted in Riley 1989: 8) 
- "My Ice House is about 18 feet deep and 16 square, the bottom is a Coarse Gravell & the water which drains from the ice soaks into it as fast as the Ice melts, this prevents the necessity of a Drain which if the bottom was Clay or Stiff Loam would be necessary and for this reason the side of a hill is preferred generally for digging an Ice House, as if needful a drain can easily be cut from the bottom of it, through the side of the Hill to let the Water run out. The Walls of my Ice House are built of stone without Mortar (which is called Dry Wall) untill within a foot and a half of the Surface of the Earth when Mortar was used from thence to the Surface to make the top more binding and Solid. When this Wall was brought up even with the Surface of the Earth I stopped there and then dug the foundation for another Wall, two foot back from the first and about two foot deep, this done the foundation was laid so as to enclose the whole of the Walls built on the inside of the Hole where the Ice is put and on this foundation is built the Walls which appear above ground and in mine they are about ten foot high. On these the Roof is fixed, these walls are very thick, built of Stone and Mortar, afterwards rough Cast on the outside. I nailed a Cieling of Boards under the Roof flat from Wall to Wall, and filled all the Space between that Cieling and the Shingling of the Roof with Straw so that the heat of the Sun Cannot possibly have any Effect.
- "In the Bottom of the Ice House I placed some Blocks of Wood about two foot long and on these I laid a Plat form of Common Fence Rails Close enough to hold the Ice open enough to let the Water pass through, thus the Ice lays two foot from the Gravel and of Course gives room for the Water to soak away gradually without being in contact with the Ice, which if it was for any time would waste it amazingly. . . .
- "I find it best to fill with Ice which as it is put in should be broke into small pieces and pounded down with heavy Clubs or Battons such as Pavers use, if well beat it will after a while consolidate into one solid mass and require to be cut out with a Chizell or Axe. I tryed Snow one year and lost it in June. The Ice keeps until October or November and I believe if the Hole was larger so as [to h]old more it would keep untill Christmass, the closer it is packed the bet[ter i]t keeps and I believe if the Walls were lined with Straw between the Ice [and] Stone it would preserve it much, the melting begins next the Walls and Continues round the Edge of the Body of Ice throughout the Season."
- Cutler, Rev. Manasseh, 13 July 1787, describing The Hills (later Lemon Hill), estate of Robert Morris, Philadelphia, Pa. (1987: 1:256–57) 
- “We continued our route, in view of the Schuylkill, and up the river several miles, and took a view of a number of Country-seats, one belonging to Mr. R. Morris, the American financier, and who is said to be possessed of the greatest fortune in America. His country-seat is not yet completed, but it will be superb. It is planned on a large scale, the gardens and walks are extensive, and the villa, situated on an eminence, has a commanding prospect down the Schuylkill to the Delaware.”
William Groombridge, View of Lemon Hill, c.1800.
- Riley, John P. 1989. The Icehouses and Their Operations at Mount Vernon. Mount Vernon, Va.: Mount Vernon Ladies’ Association. view on Zotero
- Cutler, Manasseh. 1987. Life, Journals, and Correspondence of Rev. Manasseh Cutler. Edited by William Parker Cutler and Julia Perkin Cutler. 2 vols. Athens, Ohio: Ohio University Press. view on Zotero