Yes, the Voynich manuscript is worth mentioning here, but it doesn't qualify as a really big, wide-ranging and high-quality corpus: it's about 35 thousand words

Yes, the Voynich manuscript is worth mentioning here, but it doesn't qualify as a really big, wide-ranging and high-quality corpus: it's about 35 thousand words (if the things that look like words are words), whereas a million words would still be a small corpus by today's standards; it's a single document (for example, it might contain no first-person pronouns, no future tenses, almost no mention of individual people, ...); and we have no idea about the quality (for example, perhaps it was copied by someone who didn't understand it and is such a bad copy that even someone who knows the language and the script would find it hard to understand). Still, it is definitely worth mentioning here.