Classic Kolkata breakfasts (buns, omelette, tea or bakery items) are perfect before a long train leg; Flurys opens early and is a reliable option near Howrah/Esplanade.
Overnight rail from Howrah (HWH) to Jaipur — book an AC coach for comfort. Expect ~20–26 hours depending on the service; this is the long westward transfer into Rajasthan.
A sunset camel or jeep safari on the golden dunes is the highlight in Jaisalmer; half-day excursions typically run late afternoon to sunset — book ahead.