Mich. Comp. Laws § 322.452

Sec. 2. Proofs of such purchase shall be made to the commissioner of the state land office by the production of conveyances, printed or written contracts, or duly certified copies thereof, if the same shall have been recorded, or in case of loss, without record, by at least 2 disinterested witnesses satisfactory to said commissioner of the state land office of such loss or of the existence of such conveyance or contract previous to the dates mentioned in section 1. Proof of such actual and continued possession and improvements by such claimant or his grantors shall also be made to said commissioner of the state land office by at least 2 disinterested witnesses, and said commissioner of the state land office in his discretion may require the personal attendance of such witnesses or receive sworn statements of such facts.