variac options

Good day all.

I was some time ago ( 1 year ago maybe), told that a cheap option to a
variac was using 100w lightbulbs. Arrange them in a paralell way (see
drawing below) and as you turn on the bulbs that's the wattage going to the
system,  turn on the first lightbulb you get 100w in, turn on the second
light bulb on let the first one on and you'll get 200w in etc, when you
finish turning all the lightbulbs on, turn off the lightbulb bank off and
turn on the main switch on.  

Is this correct, that's the way I understood it. Does anyone have any
comments or sugestions, drawbacks on using this setup ???

AC______________________> to neon trans.
                  main switch                 
AC_________/  ___________>to neon trans.
        I           I   
            /               I
            I               |      <---- light bulb bank
        I--100w--/  -I
        I--100w--/  -I
        I--100w--/  -I
        I-- etc..--/  -I