Look - we found "E" (for Earth) and "S" (for Science) on rocks! And we already knew that Earth Science rocks! Actually, these compass directions are part of the markers in the Stopford Family Meadow Maze at Tyler Arboretum (link is external) [4] in Media, PA.
Links
[1] https://www.paesta.psu.edu/sites/default/files/geophoto/esrock.jpg
[2] https://www.paesta.psu.edu/earth-science-image/anthrosphere
[3] https://www.paesta.psu.edu/earth-science-image/lithosphere
[4] http://www.tylerarboretum.org/