Hi Obmar,
The reason i specified 1 watt resistors is that they can handle about 1 kV each.
A ¼ Watt resistor will have a flashover at about 200 Volts.
So to measure a very high voltage the resistors need to be soldered in a chain, preferrably spaced apart to avoid flashovers and 1 Watt or more to have enough body length of each resistor.
For a voltage measurement with a DMM a very small current is needed so the power rating of 1 Watt should be adequate to provide you with a test current of < 1 mA.
We use 10 kV testers at work which use a series resisitor of 80 M
hm: consisting out of 24 x 3.3 M
hm: 1 watt R's in series. to drive a volt meter 0 - 10 kV dc.