So I dug up my library on beauty care. It spans a long way back. Here's instructions from an 1873 Young Ladies' Journal on how to wash the hair:
It is occasionally necessary to thoroughly cleanse the hair. One or two precautions must be taken, however. Never use soap if you can avoid it; if you do, let it be the very mildest and unperfumed. Avoid so-called hair-cleansing fluids, and use rain-water filtered. The yolks of two new-laid eggs are much to be preferred to soap; they make a beautiful lather, and when the washing is finished, and the hair thoroughly rinsed in the purest rain-water, you will find, when dry, that the gloss will not be destroyed, which an alkali never fails to do. The first water must not be very hot, only just warm, and the last perfectly cold. Dry with soft towels - but do not rub till the skin is tender - and afterwards brush. Be always careful to have your brushes and combs perfectly clean and free from grease.
If this is too much girliness for you, take this quiz. It tells you which famous Western feminist you most resemble. If you are a man, you must first take a few deep breaths, imagine yourself to be a woman, and then rapidly answer the questions. I am Simone de Beauvoir, with a dingleberry named Sartre dragging behind me. Link to the quiz via Going Dutch.
Postscript: I just realized why the water must be so cool: Imagine your hair with a couple of egg yolks in hot water! Anyone who's thickened a sauce with egg yolks would know what would happen. Wet hair encircled by slimy globs of semi-cooked egg!