Mo. Rev. Stat. § 442.360: Powers of attorney, how acknowledged and proved.

Every letter of attorney or other instrument containing a power to convey real estate, as agent or attorney for the owner thereof, or to execute, as agent or attorney for another, any instrument in writing conveying real estate, or whereby real estate may be affected in law or equity, shall be acknowledged or proved, and certified and recorded, as other instruments in writing conveying or affecting real estate are required to be acknowledged or proved and certified and recorded.