Lygia Clark, Caminhando / 1964, from Formless by Y-A Bois and R Krauss
A Mari Andrews Installation / 2003 (from her site)
Richard Long's Karoo Crossing / 2004, from his site
"Knots owe much of their importance in folklore to their immense antiquity.
It is possible that except for sticks and stones they may be man's oldest tool..
Analogous achievements of birds and apes support the hypothesis that men
must have needed knots, and known how to tie them, at an exceedingly
early stage in evolution."
/ "Knots and Knot Lore," Cyrus Day
"There were anciently sacred piles of stones called by the Greeks hillocks of
Mercury... placed by the sides or in the points of intersections of roads; where
every traveller that passed threw a stone upon them."
/ Symbolical language of ancient art and mythology by RP Knight and A Wilder