1. Opium in a luxurious opium den in the late 1800s.
To me, this would be the pinaccle of relaxtion - being served the highest grade opium by attentive and knowledgeable servers, relaxing my head on a silk pillow, inhaling that beautiful floral smoke with opulence all around me. When I used to be nodding hard, I'd laugh to my self sometimes picturing myself in an opium den, then coming out of the nod and seeing the disgusting filth around me. The irony always made me laugh.
2. Heroin, from Bayer Co., preferably mail ordered from the Sears catalog.
Around the turn of the century (1900), you could actually mail order a 'Heroin kit' from Sears. It came in a small carrying case and had a couple of outfits and a vial of Bayer brand Heroin (tm). The irony of it aside, that high to be some fire shit. LOL
3. Ms. Winslow's Soothing Syrup
This was from the patent drug era too, and was specifically marketed towards children. Guessing it had a sweet sugary taste to it. It also was packed with morphine. I always thought it sounded soothing as hell personally.