Guenevere gave this garment to Alexander of Greece when her husband dubbed him knight. It was of white silk, sewn entirely with gold or silver thread, except that Soredamors, who helped sew it, had worked some golden hairs from her own head in beside the metallic threads to see if she could ever find a man able to tell the difference. The metallic gold threads eventually tarnished as Sir Alexander wore the shirt, while the hair became lovelier.
At length Guenevere, making a conversation piece of the shirt while Alexander was wearing it one evening in company with her, Soredamors, and his own companions, divined the love between him and her handmaiden, whom she prodded to reveal her part in making the shirt.
When Alexander learned this, the garment became infinitely more valuable to him than before, and he treated it as a wonderful relic. While having no other special properties, it helped lead to the lovers’ brief but happy marriage.
Source
Cligés | Chrétien de Troyes, late 12th century