Found it! Things of Science: http://ecg.mit.edu/george/tos/ http://ecg.mit.edu/george/tos/ for the price of 5$/year. [edit: looks like I misremembered though,

Found it! Things of Science: http://ecg.mit.edu/george/tos/ http://ecg.mit.edu/george/tos/ for the price of 5$/year. [edit: looks like I misremembered though, neither the Make article nor the website mention radioactivity... must have got it mixed up with something like this: https://en.wikipedia.org/wiki/Gilbert_U-238_Atomic_Energy_Laboratory https://en.wikipedia.org/wiki/Gilbert_U-238_Atomic_Energy_La...]