Perhaps there was a 'joke' comparison that that author forgot or later editors deemed unserious. Something like "only a mass equivalent to the Himalayas, less

Perhaps there was a 'joke' comparison that that author forgot or later editors deemed unserious. Something like "only a mass equivalent to the Himalayas, less than one billionth, would have decayed into thallium." This example is for demonstration only, as I'm not sure what the equivalent would be.