Simplify the following text for a Grade 18 native English-speaking person.
Original: One Scottish writer described his Highland countrymen this way : They greatly excel the Lowlanders in all the exercises that require agility ; they are incredibly abstemious , and patient of hunger and fatigue ; so steeled against the weather , that in traveling , even when the ground is covered with snow , they never look for a house , or any other shelter but their plaid , in which they wrap themselves up , and go to sleep under the cope of heaven .
Simplified: They greatly excel the Lowlanders in all the exercises that require agility ; they are incredibly abstemious , and patient of hunger and fatigue ; so steeled against the weather , that in traveling , even when the ground is covered with snow , they never look for a house , or any other shelter but their plaid , in which they wrap themselves up , and go to sleep under the cope of heaven .