The Collaborative International Dictionary of English v.0.48:

Caution \Cau"tion\ v. t. [imp. & p. p. Cautioned; p. pr. & vb.
   n. Cautioning.]
   To give notice of danger to; to warn; to exhort [one] to take
   heed.
   [1913 Webster]

         You cautioned me against their charms.   --Swift.
   [1913 Webster]