Few oscilloscopes will allow full mains voltage to be rammed down their inputs, let alone some of the higher standard voltages found. Sorry, what was that....... for those who never heard that comment, he said he uses a 10:1 scope probe. Shucks!, you really do want to make me nervous!
Scope probes, including 10:1 types, have a very low acceptable working voltage. Most don't boast much more than 100Vpeak. The only solution is to create our own acceptable, safe, attenuating 'scope probe'. These are covered later in the section "measurement aids". Using them is covered here.