Mari and Waka plan on making a cake for their friend, but plans fall apart when Mari opens a mysterious book that sends her flying back in time where she ends up crossing paths with William Gilbert.
and it's a device for measuring the angle 
between the horizon and the north pole.
y es un dispositivo para medir el ángulo
entre el horizonte y el polo norte.
É um dispositivo para medir o ângulo
entre o horizonte e o polo Norte.