Olive Size is the amount necessary: Shabbat 83b
Size of receiving-materials, for communication of Impurity from a Corpse: Shabbat 79a
How much of the spine must be missing, to remove the potential to communicate standard impurity inside a rooved structure: Eruvin 7a
How much of the skull must be missing, to remove the potential to communicate standard impurity inside a rooved structure: Eruvin 7a
