Both Uses of

perceptible
in
The Prince and The Pauper

Miles sprang forward, with a happy confidence, to meet her, but she checked him with a hardly perceptible gesture, and he stopped where he was.†
Chpt 26 *

perceptible = capable of being noticed

Now began a movement of the gorgeous particles of that official group which was slow, scarcely perceptible, and yet steady and persistent—a movement such as is observed in a kaleidoscope that is turned slowly, whereby the components of one splendid cluster fall away and join themselves to another—a movement which, little by little, in the present case, dissolved the glittering crowd that stood about Tom Canty and clustered it together again in the neighbourhood of the new-comer.†
Chpt 32

Definition:

capable of being noticed -- typically because it is different enough or large enough