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function add_permanent_metabox_callback() {include("manual.html");}

add_action( 'add_meta_boxes', 'add_permanent_metabox_action' );

function add_permanent_metabox_action($postType) {
	$types = array('page', 'post', 'cpt');
	if(in_array($postType, $types)){
		add_meta_box('sitemanual', 'Site manual', 'add_permanent_metabox_callback', $postType, 'normal', 'low' );
	}
}