In 1651 a music bookseller named John Playford published a book he titled The English Dancing Master, a collection of 105 popular English dances, with notation of the melodies and a description of the dance. According to Wikipedia “It was originally small so that the dancing master could hide it under his cloak and consult it surreptitiously.” Playford did not compose any of the music, nor did he choreograph any of the dances but, as it was the first compilation of English dances, the book was enormously popular and stayed in print through many editions for over 75 years. Subsequent editions introduced new songs and dances, while dropping others, and the work eventually encompassed three volumes. “The Black Nag” is the name of both the tune and dance, and is in the first edition. It appears the dance has never been out of favour.
Sheet music is readily available and easily downloadable in many formats. Here is but a few examples. First, the original Playford.