Mich. Comp. Laws § 41.70
The supervisor, 2 trustees, the township treasurer, and the township clerk constitute the township board, and any 3 of them constitute a quorum for the transaction of business at a meeting of the township board. However, in townships having a population of 5,000 or more as determined by the last federal decennial census or having 3,000 or more registered electors, the supervisor, the township treasurer, the township clerk, and 4 trustees, to be elected by the registered electors of the township as provided in sections 358 and 362 of the Michigan election law, Act No. 116 of the Public Acts of 1954, being sections 168.358 and 168.362 of the Michigan Compiled Laws, constitute the township board, and any 4 of them constitute a quorum for the transaction of business. The township clerk in such a township shall be the clerk of the township board. However, this subsection does not apply unless the electors of a township having a population of 5,000 or more, or having 3,000 or more registered electors, adopt the provisions of this section by a majority vote at an annual or special township meeting of the electors or adopted the provisions of this section before December 22, 1952.
MCL 41.70