Although the History section asserts that this cocktail was not featured in Boothby’s own publications, I was actually able to find it in this 1934 (posthumous, I suppose?) edition of Boothby’s World Drinks: https://euvs-vintage-cocktail-books.cld.bz/1934-Cocktail-Bill-Boothby-s-World-Drinks-and-how-to-mix-them1.

The cocktail is listed under “Manhattan, Boothby” on p. 108. The proportions are largely similar to what Simon has here, but I do note an extra dash of orange bitters.

I also enjoyed hearing about this classic California figure — he certainly fit right in with many of the loony personalities in turn-of-the-century San Francisco. Looking forward to trying this once I have the need to pop open a bottle of bubbly!