Time to get Medieval

As the two girls opened the door, what they saw was a large room that appeared to be made of stone full of rough approximations of medieval **** devices that all stood empty. There were several devices including a stretching rack, an iron maiden, a pillory, an iron chair, and a wooden horse. As Samantha looked at the items, she could have sworn that the last one wasn't a **** device at all though. As they entered and the door swung shut behind them, a timer on the wall began counting down from 30 minutes, a table in the middle seemed empty save for a scroll.

Rachel immediately stepped forward. "Okay so we have 30 minutes until the doors are opened. Don't worry, my group nailed this one already so we should be fine." As she went to the table and grabbed the scroll, her eyes scanned it before ultimately coming to a conclusion.

"Shit."

Samantha felt her confidence evaporate like snow in the sun. "Shit? What do you mean Shit?"

Rachel turned and handed her the scroll. "They changed it. This is a different riddle than what we did before. Take a look."

Taking the scroll, Samantha read over the riddle on it carefully.

'What is stronger than steel but can't handle the Sun?'

"Endure the correct trial to receive the key to the door and don't run out of time. Each trial lasts ten minutes. Good luck."

"Okay, so what do we do with this?"

Rachel pointed to each of the devices which had an emblem on a mat in front of them. The pillory had the symbol of stone, the iron maiden, the symbol of ice, the pillory had the symbol of fire, the wooden horse had a symbol of air, and the iron chair had a symbol of a lightning bolt in front of it.

"Samantha, I'm not familiar with this riddle. Any ideas?