I was working on a circuit tonight, and made the mistake of letting one of my friends use the DMM for me. While it wasn't needed, he decided to measure his "Brain voltage", i.e. touch a probe to each ear... well I'll be darned if it didn't register 20mV. We repeated this test, including assuring ourselves that the DMM was functioning correctly, by measuring a known source. His head continued to show up as 20mV, other objects, a table and a chair, or two points on the same table, registered as 0V...
Very odd if you ask me. Do any of our sages know the answer (Nigel?)?