Firstly, I'll raise my hand to say that in my earlier days, about two decades ago, weighing my doses was never a concern for me, so I don't want to appear too hypocritical in frowning at the latter suggestion. 'Feel' might be a difficult thing to judge for newcomers to the experience.Yup. And then vacuum distilled DMT will be a quarter of the volume as the one on the right there!
I think DMT you can get away by feel. Just don't vape the entire amount in one hit.
Maybe my by feel is bias... as I did weigh the DMT before. So I have general idea of what 15-20mg is.