The Board of Supervisors may call a special meeting of the District whenever a majority of the Board of Supervisors shall deem it necessary or prudent so to do, and shall call a special meeting of the District upon receipt of a petition signed by at least five percent of the legal voters of the District. The Board of Supervisors may rescind the call for a special meeting called by it, but may not rescind the call for a special meeting by petition. A special meeting called for by petition shall be held within 60 days of receipt of the petition by the Board of Supervisors.