We study a characterization of slice Carleson measures and of Carleson measures for both the Hardy spaces Hp(B) and the Bergman spaces Ap(B) of the quaternionic unit ball B. In the case of Bergman spaces, the characterization is done in terms of the axially symmetric completion of a pseudohyperbolic disc in a complex plane. We also show that a characterization in terms of pseudo-hyperbolic balls is not possible