Solidified Paint Markers such as Sakura Solid Markers are liquid paint with all the solvents squeezed out by a heated curing process. The finished product has no solvent content since the solvent has been evaporated completely in the curing process. These are excellent for marking all surfaces permanently. Solid markers are not, however, crayons.
Technically speaking, a crayon contains a lot of clay and extenders and so don't leave much room for pigments as much as solidified paint. Removable wax crayons and lumber crayons fall in this category. In order to retain durability to the mark, they work best on concrete and raw lumber.
Products such as Sharpie Peel Off Pencils, Mitsubishi® Dermatograph, and Mistubushi® Rainbow are China Markers. These are wax based pencils that have a similar make up to traditional crayons but they are thinner and are encased in a peel off pencil.