Sentence:  "Crato" in a conſultation of his for a noble patient, tels him plainly, that if his Highneſſe will keepe but a good diet, hee will <WSD>warrant</WSD> him his former health. 
Meaning of the word marked with <WSD> tags:  To give (someone) an assurance or guarantee (of something); "also, with a double object": to guarantee (someone something).