[Oldcodger]

There's two considerations here. Do you use a neon which only needs one hand at the end of a tester connected to what may/may not be a lethal supply. Or use a meter with both hands on either side ( and a path across the heart) overthe voltage .( unless you can secure one terminal to a neutral /earth voltage first) . I was indoctrinated into proving by my ancient uncle a time served electrician, who insisted on only one hand contact . BUT the problem with all test kit ( including the neon ) is lack of proving the tester on a known live circuit first.
me- I'm not an electrician, just a bloke who's worked on ,and been tested on high voltage working methods ( up to 650 v DISTRIBUTION) , up to 1000v Ac ( anyone remember CEL 6 ) and a few UK-other countries submarine cable systems of up to 4500 v.