As I walk up from the Oakland subway station on a Sunday morning, rain is falling in a slow drizzle and the downtown street is deserted. Around the corner, I spot the “Tropicana Ballroom” sign on a 1920s building that is my destination. I pay $15 at the entrance and walk up the red-carpeted stairs to a ballroom where art deco wall sconces softly glow onto an 8000-square-foot floor full of dancers warming up. On the far side of the dance floor, beneath floor-to-ceiling windows, an altar has been laid with candles, a vase of gladiolas, a statue of Shiva, and Osho Zen Tarot cards. A young woman sits cross-legged in meditation in front of the altar; the man next to her is kneeling and praying; and two hundred other dancers—ranging in age from infants wearing padded ear coverings to men and women in their 70s—are preparing to “sweat their prayers” on the dance floor.