This is what it is called from the main page:
import { Component } from '@angular/core';
import { NavController, NavParams } from 'ionic-angular';
import L from "leaflet";
Use the reference to this page: link
Thank you very much I had to install it again and it just worked, and now it runs, install it outside of my project that's why I did not recognize, install the following command in my project:
npm install leaflet --save
Thanks to everyone
Hello for the error does not find the library, the most possible is that you have not installed.
npm install -S leaflet