#1 "up" & #2 "up" = off. Otherwise SPST switches would work (and
you coudn't turn the light both on and off from either end).

S #1 "up" S #2 "down"
S #1 "down" S #2 "up"



or Switch #2 "



A switch circut with two spdt switches has two on states,
and two off states. I like them set up so the
light is on whenever the two switches are in the same
position.