What did Madam C. J. walker create?

In the early 1900's Madam C.J. Walker created a temporary method of hair relaxing it wasn't done by using chemicals, it was done by pressing the hair.
Pressing the hair was done by applying petroleum jelly to the hair and then it was straighten by applying a metal hot comb through it.
The hot comb was placed on a stove, nowadays you can purchase this set that comes with a hot comb and a mini stove used by beauticians today.
It was then tested with tissue paper for the proper temperature, if it was to hot the tissue turned brown. You know not to apply it to the hair until the hot comb cools down.
You ran the hot comb through the hair by parting the hair in sections starting from the nape and working your way up.