A Horse is a Horse

A little tid-bit from the Schott's Miscellany daily calendar my now-Mother-in-Law got me for Christmas last year:



A horse will live 25 days on water without solid food, 17 days without eating or drinking, but only 5 days on solid food without drinking.

-- Burroughs' Encyclopaedia of Astounding Facts and Useful Information, 1889

Two things struck me about this:
(1) Doesn't it sound strikingly like a logic problem where you're going to be asked how little you could feed and water the horse over a period of 30 days without it dying?
(2) Who in the world tested these theories??? Maybe in 1889 it was trial by error.