According to "A New Universal History of the Religious Rites, Ceremonies and Customs, of the Whole World, Or, A Complete and Impartial View of All the Religions in the Various Nations of the Universe, Both Ancient and Modern, from the Creation Down to the Present Time" (wordy title...), by William Hurd, 5th edition, published 1814:
"The feast of Purim, which signifies lots, continues two days; and it was first instituted in memory their deliverance from destruction, when Haman instigated Ahasuerus to put them all to death. In the morning they give bread to the poor, and in the evening they repair to the synagogue, where the whole book of Esther is read over, and explained to the people at large.
"During the reading of this lesson, the reader kneels, whereas he is obliged to stand when he reads the law, and he repeats three prayers, wherein he blesses God for having delivered them from the plot formed against them by Haman Prayers being over they indulge themselves in all sorts of luxury; so that this may be justly called the Jewish carnival."
I'm laining part of the Megillah this Purim. Better buy myself some kneepads!