Montessori classrooms encourage hand work for their students. Knitting is a wonderful craft and a hands on intellectual experience. Each time you knit, you really are tying a knot.
Knitting introduces basic math and geometry. When knitting, you have to divide stitches, add stitches, and subtract stitches. Also, the strings of yarn turn into geometric shapes.
There is a branch of math called knot theory, so let your children keep on tying knots.

Visit wiki.montessorimom.com for great links for finger knitting, knot tying, and knitting.