Couldn't accomplish this in a comment to Rahul's #1, but here is a physical realization of my drawing with colored pencils. Compare: ![alt text][1] ![alt text][2] The pencils are in contact, but the lead inside could serve as lines in space without contacts. I don't know how to reconcile this with your quote from Whiteley... [1]: https://i.sstatic.net/mXuKC.jpg [2]: https://i.sstatic.net/6ceaA.jpg