There is no one rule or set of rules for citing primary sources in the Chicago Manual of Style; the format of the note and bibliographical entry will depend on the type of material from where the source originates. The links below will provide guidance for how to craft citations for primary sources based on type.
While it is generally discouraged, it is possible to cite a source taken from a secondary source. If an original source is otherwise unavailable, it is cited as "quoted in..." and both the original and secondary sources must be listed.
1. E.E. Cummings, "A Poet's Advice to Students," Ottawa Hills Spectator, October 26, 1955, quoted in George J. Firmage, ed., E.E. Cummings: A Miscellany Revised, (New York: October House Inc, 1965), 335.
Cummings, E.E. "A Poet's Advice to Students." Ottawa Hills Spectator, October 26, 1955, quoted in Firmage, George J., ed. E.E. Cummings: A Miscellany Revised. 335. New York: October House Inc, 1965.
Legal and public documents, including court cases, legislation, and other government documents have special citation forms based on The Bluebook: A Uniform System of Citation. CMS accounts for certain basic rules of citation, but defaults to The Bluebook. A copy of this guide is available in the Bates Reference collection on the first floor.