It's a good job Khal Drogo has the hottest fire and most efficient cook pot in the realm otherwise Viserys' execution would've been an all-round pretty awkward experience for everyone involved. Viserys demands a golden crown, and Drogo obliges. He tosses gold medallions into a pot, and five seconds later, they're a gloopy liquid. That's just impossible. In reality the fire would've had to be far hotter, and Viserys held in position for far longer than just a few seconds as the gold became pourable.