R - How to draw an empty plot with no height?

R - How to draw an empty plot with no height?

I can make an empty plot in R by using:
plot.new()
That create a blank plot with the default width and height.
I want to create an empty plot with minimal height. I tried png('z.png',
height=1), but that got me:
> png('x.png', height=1)
> plot.new()
Error in plot.new() : figure margins too large
How can I create such a plot? I guess I have to zero the margins too.