Mary Gertrude Haseman found all 12-crossing and many 14-crossing amphicheiral knots in the late 1910s.
[3][4] But a counterexample to Tait's conjecture, a 15-crossing amphicheiral knot, was found by Jim Hoste, Morwen Thistlethwaite, and Jeff Weeks in 1998.
[5] However, Tait's conjecture was proven true for prime, alternating knots.
No knots with crossing number smaller than twelve are positive amphicheiral and noninvertible .
[8] If the self-homeomorphism, α, reverses the orientation of the knot, it is said to be negative amphicheiral.