Actually it depends on the year. The 2000 lbs given above is the most accurate, but that is PAYLOAD which needs to include passengers and gear etc... It's not the amount of weight you can put in the bed of the truck on top of everything else. It's everything you put into the truck minus a full tank of gas. That's 2000 lbs, and with two 150 lb guys your available payload becomes 1700 lbs. TheTundra is not a 1 ton truck unfortunately... More like a half ton. I still love it though!
Payload also includes fuel. I get a ton of heating pellets twice a year. The store i buy them at is about 5 miles away and I split it into two trips. 1000 lbs and I hit the bump stops often. It is loaded over the rear axle and back. If I wanted it to handle better I would have to load it in the front of the bed.
Let's remember what good sense tells us. If you are going less than a mile at 20 mph with no traffic around, you can probably carry 2,000 lbs in the bed. Just be really careful.
If you will drive in normal traffic ( including on the highway), taking curves and hitting the brakes hard, then you should not overload your truck as not only you can damage it, but you can very well lose control and hurt yourself and others.
Think about safety as we are in a highly litigious society and any such dumb move can cost you plenty.
I have hauled over a ton in the bed of my truck a few times(dirt, rocks, and landscaping blocks). The trips are always about 20 miles from anywhere to buy them. So I just drive a little slower than I usually do and make sure and give myself plenty of room. I wouldnt recommend hauling over 2000 just because the front end will start gettting light and squirrly. I do not do this anymore because now I have a 16ft trailer to carry all my junk on.