I have shot way beyond the metric prefixes Giga and Tera. I've more than doubled the magnitude of my prefix ability because my Thursday student's physics book introduced the prefix Yotta. It means 10^24 power. As a weird coincidence, if you convert the weight of the earth into grams, the earth weighs about a yottaGram. So, in the same sense that a reference for the meter can be kept in a vault in Paris, so can the reference item for one yottaGram be kept somewhere. It is the whole earth.