Definition of "sagacity"

Young ladies have great penetration in such matters as these; but I think I may defy even your sagacity, to discover the name of your admirer.

1813 January 27, [Jane Austen], chapter 15, in Pride and Prejudice: […], volumes (please specify |volume=I to III), London: […] [George Sidney] for T[homas] Egerton, […]

Immediately after the meal, when he was alone again, he set to work to examine Drayton’s papers, of which there lay quite a mass on the table near him and, leaning toward the lamp on his elbow, he weighed the meaning of each with a certain sideward sagacity of gaze, a sagacity that smiled in its self-sureness.Swiss Family Robinson- "....near the mouth of a creek, towards which all our geese and ducks betook themselves; and I, relying on their sagacity, followed in the same course."

1904, M. P. Shiel, The Evil That Men Do‎, London: Ward, Lock & Co., Chapter

[…] this Beast [the Ichneumon] is not only enemy to the Crocodile and Asp, but also to their Egs, which she hunteth out by the sagacity of her nose, and so destroyeth them […]

1607, Edward Topsell, The History of Four-footed Beasts, Serpents, and Insects‎, London: G. Sawbridge et al., published 1658, page 352