Oscar Wilde's play The Importance of Being Earnest contains the following lines (shortened as marked for this purpose) in its third act:
JACK. I beg your pardon for interrupting you, Lady Bracknell, but this engagement is quite out of the question. I am Miss Cardew’s guardian, and she cannot marry without my consent until she comes of age. That consent I absolutely decline to give.
LADY BRACKNELL. [To Cecily.] Come here, sweet child. [Cecily goes over.] How old are you, dear?
CECILY. Well, I am really only eighteen, but I always admit to twenty when I go to evening parties.
LADY BRACKNELL. [...] Eighteen, but admitting to twenty at evening parties. Well, it will not be very long before you are of age and free from the restraints of tutelage. So I don’t think your guardian’s consent is, after all, a matter of any importance.
JACK. Pray excuse me, Lady Bracknell, for interrupting you again, but it is only fair to tell you that according to the terms of her grandfather’s will Miss Cardew does not come legally of age till she is thirty-five.
CECILY. Algy, could you wait for me till I was thirty-five?
From what I've found, the legal age (for self-decided marriage) at that time was 21 (and this is actually indirectly referenced by Bracknell). I could understand if the inheritance of the grandfather was only made available by the age of 35 (but that wouldn't really make any sense, as it would pose a problem unsolvable by Jack's consent), but was it actually possible to alter the legal age of marriage in such a way? Or is it just artistic licence on Wilde's part?