Tektronix 434 s/n below 500000 faulty ps.

[Nick]

...For example, if you have a 100 1M 0.5W resistors kicking around you could build a 100M chain with a maximum voltage rating
of around 300kV - but I wouldn't really recommend it!

Only if it's embedded in dry HV oil or SF6 and the layout is very carefully maintained !