William Duane, A military dictionary
“ Letter, in its general acceptation, a character such as forms the alphabet, or any thing written, such as an epistle, &c.Letter of attorney, an instrument in writing, authorizing an attorney, or any confidential person, to take the affairs of another in trust. A letter or power of attorney is necessary to empower a person to receive the half-pay of an officer. This should be accompanied by a certificate sworn to by the officer before some magistrate or justice of the peace. ”
