The heating setup is still used today. In fact, you can get integrated components called OCXOs (Oven Controlled Crystal Oscillator) that do the whole job in one

The heating setup is still used today. In fact, you can get integrated components called OCXOs (Oven Controlled Crystal Oscillator) that do the whole job in one small package with precision over time on the order of 1ppb. Cheaper, and less precise, are TCXOs (Temperature Compensated Crystal Oscillators) where a crystal is paired with a circuit that has an opposite dependency on temperature so that the errors tend to cancel each other out.