Thereafter they voyaged till they found a great silvern column. It had four sides, and the width of each of these sides was two oar-strokes of a the boat, so that in its whole circumference there were eight oar-strokes of the boat. And not a single sod of earth was about it, but (only) the boundless ocean. And they saw not how its base was below, or because of its height how its summit was above. Out of its summit came a silvern net far away from it; and the boat went under sail through a mesh of that net. (Source)
In this story Mael Duin travels to various magical islands. On one of them he finds a silver column that is so high that they cannot see the top or bottom. From the summit a net hangs down. Perhaps it is the starry sky hanging down from the World Pillar. A nice image.