Perfect Silicon Sphere to Redefine the Kilogram
I remember a small magazine (called Science Digest, IIRC) I read in the mid 80's. It was short little science articles, probably a couple hundred words each (at most)...not unlike RSS feeds today, perhaps.
One article was about scientists making the most perfect sphere to date out of some crystal. It was measured to be so perfectly round that if you scaled it up to the size of the earth, it's highest peak would be 12 feet higher than it's lowest point.
I'm sure the technology for this thing has improved a lot in 20 years.