Summon item not working

I'm making an adventure map, and at some points I need there to be items on the ground. But when I use the /summon command, it always ends up as a stone block.

Here's what I've used:

/summon Item ~ ~ ~ {Item:{id:276,Count:1,tag:{display:{Name:"Mirage"},Unbreakable:1},Damage:0}}

This did not work, so I tried a simpler command:

/summon Item ~ ~ ~ {Item:{id:276,Count:1,tag:{},Damage:0}}

Which also summoned a stone block. Please note that I am in the Minecraft 1.9 snapshot 16w05b

Solution 1:

Item number 276 does not exist in 1.9

Minecraft slowly moved away from numeric IDs for items for some time now, mostly because they are a hassle to remember. While previous versions such as 1.8 still allowed you to use numerical ids, you have to use the named ids starting with 1.9.

In your case, that is minecraft:diamond_sword, e.g.:

/summon Item ~ ~ ~ {Item:{id:minecraft:diamond_sword,Count:1}}