Thomas Blount's 1656 hard-word dictionary that when published was the largest English dictionary at that time (it defined about 11,000 words). It was the first to include etymologies and to cite sources for its definitions.
Glossographia's title page
1. It was immediately surpassed in popularity by Edward Phillips' The New World of Words (1658), which defined about 20,000 words.
Example - Some example entries are:
"Alliteration, a figure in Rhetorick, repeating and playing on the same letter."
"Paragogical, of or pertaining to the figure Paragoge, which is when a syllable or letter is added to the end of a word."
"Sesquipedalian words (verba sesquipedalia) used by Horace for great, stout, and lofty words; words that are very long, consisting of many Syllables."