169.9—Connection with natural objects.
When the distance to an established corner of the public survey is more than 6 miles, this connection will be made with a natural object or a permanent monument which can be readily found and recognized, and which will fix and perpetuate the position of the terminal point. The maps must show the position of such mark, and course and distance to the terminus. There must be given an accurate description of the mark and full data concerning the traverse, and the engineer's affidavit and the certificate on the maps must state the connections.