Section 194
SEC. 194. Appraisers are hereby authorized to call before them and examine, upon oath or affirmation, any owner, importer, consignee, agent, or other person, touching any matter or thing which they may deem material respecting any imported or exported merchandise in determining the duty thereon, and to require the production of any letters, accounts, or invoices relating to such merchandise, and such testimony may be reduced to writing, and if so shall be filed with the collector.