In doing more research on morning dress, and wedding fashion in particular, I read portions of Emily Post’s Etiquette in Society, in Business, in Politics and at Home
(published New York: Funk & Wagnalls Company, 1922). This book is quite informative for what was “proper” in America at the time. I am unsure how much of this applied to other parts of the world.
The reason I mention this, is that she mentions the use of a “white piqué double-breasted waistcoat”. It is good to know that my intention for wearing a white double-breasted waistcoat was considered “proper” or “the norm” at one point. Though I had never heard of a piqué waistcoat with daywear.
In "The Wedding Clothes of the Bridegroom" from Chapter XXI, "First Preparations before a Wedding", she says:
If he does not already possess a well fitting morning coat (often called a cutaway) he must order one for his wedding. The frock coat is out of fashion at the moment. He must also have dark striped gray trousers. At many smart weddings, especially in the spring, a groom (also his best man) wears a white piqué high double-breasted waistcoat, because the more white that can be got into an otherwise sombre costume the more wedding-like it looks; conventionally he wears a black one to match his coat, like the ushers. The white edge to a black waistcoat is not, at present, very good form.
Later in “Formal Afternoon Dress” from Chapter XXXIV, “The Clothes of a Gentleman”, she says:
Formal afternoon dress consists of a black cutaway coat with white piqué or black cloth waistcoat, and gray-and-black striped trousers.
What are your thoughts on using piqué for a waistcoat with morning dress?