The online Beagle library now allows anyone to see the amazing range of visual imagery that Darwin poured over during the voyage. See the illustrations here Humboldt's illustration of his famous ascent of Mount Chimborazo in the Andes in 1802.
And it may be our busy lifestyle that keeps us from napping. While naps do not necessarily make up for inadequate or poor quality nighttime sleep, a short nap of 20-30 minutes can help to improve mood, alertness and performance.
How Much Should You Exercise and How Often? Aim for at least 150 minutes a week of moderate-intensity activity (such as brisk waking). That amounts to about 30 minutes a day at least 5 days a week. If you're just getting started, you can slowly build up to that. In time, you can make your workouts longer or more challenging. Do that gradually, so your body can adjust. When you work out, keep your pace low for a few minutes at the start and end of your workout. That way, you warm up and cool down each time. You don't have to do the same exact thing every time. It's more fun if you change it up.