From Chapter 26 of Elizabeth Gaskell's Life of Charlotte Brontë (1857):
When Easter, with its duties arising out of sermons to be preached by strange clergymen who had afterwards to be entertained at the Parsonage, -- with Mechanics' Institute Meetings, and school tea-drinkings, was over and gone; she came, at the close of April , to visit us in Manchester. We had a friend, a young lady, staying with us. Miss Brontë had expected to find us alone; and although our friend was gentle and sensible after Miss Brontë's own heart, yet her presence was enough to create a nervous tremour. I was aware that both of our guests were unusually silent; and I saw a little shiver run from time to time over Miss Brontë's frame. I could account for the modest reserve of the young lady; and the next day Miss Brontë told me how the unexpected sight of a strange face had affected her.
It was now two or three years since I had witnessed a similar effect produced on her, in anticipation of a quiet evening at Fox-How; and since then she had seen many and various people in London: but the physical sensations produced by shyness were still the same; and on the following day she laboured under severe headache. I had several opportunities of perceiving how this nervousness was ingrained in her constitution, and how acutely she suffered in striving to overcome it. One evening we had, among other guests, two sisters who sang Scottish ballads exquisitely. Miss Brontë had been sitting quiet and constrained till they began "The Bonnie House of Airlie," but the effect of that and "Carlisle Yetts," which followed, was as irresistible as the playing of the Piper of Hamelin. The beautiful clear light came into her eyes; her lips quivered with emotion; she forgot herself, rose, and crossed the room to the piano, where she asked eagerly for song after song. The sisters begged her to come and see them the next morning, when they would sing as long as ever she liked; and she promised gladly and thankfully. But on reaching the house her courage failed. We walked some time up and down the street; she upbraiding herself all the while for folly, and trying to dwell on the sweet echoes in her memory rather than on the thought of a third sister who would have to be faced if we went in. But it was of no use; and dreading lest this struggle with herself might bring on one of her trying headaches, I entered at last and made the best apology I could for her non-appearance. Much of this nervous dread of encountering strangers I ascribed to the idea of her personal ugliness, which had been strongly impressed upon her imagination early in life, and which she exaggerated to herself in a remarkable manner. "I notice," said she, "that after a stranger has once looked at my face, he is careful not to let his eyes wander to that part of the room again!" A more untrue idea never entered into any one's head. Two gentlemen who saw her during this visit, without knowing at the time who she was, were singularly attracted by her appearance; and this feeling of attraction towards a pleasant countenance, sweet voice, and gentle timid manners, was so strong in one as to conquer a dislike he had previously entertained to her works.