I wrote about Frost's Notebooks before. Here is a picture of what one of them looks like:
It's from this this Website. Apparently, Frost used "fountain pens, which have thick lines and a tendency to bleed. Also, his handwriting is extremely difficult, and in the notebooks he didn’t take the same care as he would when writing a letter.”
The two pages in the picture don't show the problems with bleeding — or so it seems to me. But see also here and here.