I came upon this line of dialogue in a book I'm reading, from a character who has old-fashioned speech patterns:
できる限りの鶏肉を用意せい…
I assume this せい is some form of the verb する, though I'm not even sure if it's a regional dialect or some remnant of classical Japanese. I can find plenty of examples of the same usage on Google, but no actual explanation or grammar notes for it in any of my usual go-to sites and reference books.
Any ideas?