A lot of people have a custom of boiling 3 eggs at a time, as mentioned here, among any other places. One reason given for this practice is that if one egg turns out to be unkosher, the remaining two ...
I heard that some still have a custom to boil only odd numbers of eggs at a time. I heard that the reason is if there is a blood-spot in an egg, the egg will be Battel Berov. This only explains why ...