How to Survive a Mermaid Attack, 1527

British Library MS Royal 2 B VII, f. 97r

The mermayde is a dedely beste that bringeth a man gladly to dethe. Frome the navyll up she is lyke a woman with a dredfull face, longe slymye here a grete body & is lyke the egle in the nether parte, havinge fete and talentis to tear asonder suche as she geteth. Her tayl is scaled like a fisshe and she singeth a maner of swete song and therwith deceyveth many a gode mariner for whan they here it they fall on slepe commonly & than she commeth and draweth them out of the shippe and tereth them asonder... but the wyse maryners stoppe their eares whan they se her for whan she playth on the water all they be in fear & than they cast out an empty tonne to let her play with it tyll they be past her. This is specifyed of them that have sene it.  

Laurence Andrew, The Noble Lyfe and Natures of Man of Bestes, Serpentys, Fowles and Fisshes

The bad news is that the slimy-haired mermaid of dread wants to tear you asunder with her talons. The good news is that you can distract her with an empty barrel.

How to Care for Your Hair, 1881

Theatrical Poster, c. 1875 (Library of Congress)

“Not less than a hundred strokes a day should be given to a woman’s hair with a good hair-brush, rather hard, but not so unyielding as to tear the hair when it meets with a tangle… Once or twice a week, if possible, the hair should be allowed to flow loosely about the head for an hour or two, so as to admit of the air circulating freely about the roots… An excellent method is to rub the head thoroughly with a rather coarse towel until the healthy glow and redness ensue. If these fail to result from the rubbing, the head is in a thoroughly unhealthy and unproductive condition... The hair should never be fastened up too tightly by means of hairpins, combs, ties, &c. The sap should be allowed to circulate freely through the hair-tubes, and any cause preventing this acts prejudicially upon the growth." 

Sylvia's Book of the Toilet

Is your hair getting enough fresh air? Go on, let it free. Those hair-tubes will thank you.

How to Grow Facial Hair, 1658

"Amongst those things that will make ones beard grow, and are easy to be had, I reckon Honey, fresh Butter without Salt, the juyce of a red Onion... Badgers grease, called Das, Bears, Lions, Grease, Bryony-roots, Beets, Radish, Pepperwort, white Lilies, Flour-de-luce: a liniment may be made of these, for the chin wet with these, first brings forth a tender down, after that a thick and long beard, which that it may not grow white too soon, must be watered rather with cold water that hath a little wine mingled with it, if we desire to adorn it." 

Levinus Lemnius, The Touchstone of Complexions

The path to bearded bliss is long, tortuous, and kind of smelly. Much like the beard itself.

How to Treat Baldness, 13th century

"You're bald." "No, you're bald."
BL Royal 6 E VII, f. 197 (14th c.)

"By frequently rubbing your bald spots with ground onions, you will be able to recover the charm of your head." 

Regimen sanitatis salernitanum (c. 13th century)

This piece of advice is pretty cagey. Does the remedy actually cause your hair to return, or does an onion-greased scalp count as charming?

How to Wash Your Hair, 12th century

"Dear Past, How often should I wash my hair and what should I wash it with? Sincerely, Hair Befuddled in the Present"

Mary Magdalene
14th century, Les Enluminures

"After leaving the bath, let her adorn her hair, and first of all let her wash it with a cleanser such as this. Take ashes of burnt vine, the chaff of barley nodes, and licorice wood (so that it may the more brightly shine), and sowbread... with this cleanser let the woman wash her head. After the washing, let her leave it to dry by itself, and her hair will be golden and shimmering...  If the woman wishes to have long and black hair, take a green lizard and, having removed its head and tail, cook it in common oil. Anoint the head with this oil. It makes the hair long and black." 

The Trotula (12th century)

How frequently you should do this is not explained, but if you are going the lizard-conditioner route, my recommendation is: use sparingly.