The chief clerk of the house of representatives and the secretary of the senate are hereby directed to prepare vouchers for the state treasurer for the incidental expenses of the legislature, on presentation of certificates showing amounts due for material furnished and services rendered to dates specified. The certificates shall be signed by the speaker or president, and countersigned by the sergeant-at-arms, respectively, of the body ordering the expenditures. The state treasurer shall issue warrants which shall be in favor of and payable to the order of the persons named in said certificates.
RCW 44.04.060